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The Harvey Cushing Fund 











Copyright, 1894, 


This History has been written because of a conviction, 
from my own experience and experience with my students, 
that one of the best aids to an intelligent comprehension of 
the science of chemistry is the study of the long struggle, 
the failures, and the triumphs of the men who have made this 
science for us. The work is based upon a course of lectures 
delivered for several years past to my classes in the Uni- 
versity of North Carolina. The effort has been to systema- 
tize and digest the material on hand so as to render it 
available for those desiring a general knowledge of the sub- 
ject. Free use has been made of all the chief authorities ; 
the historical works of Kopp, Berthelot, Hoefer, Thomson, 
Ernst v. Meyer, Ladenburg, Eodwell, Muir, Wurtz, Hartmann, 
Gmelin, Karmarsch, and Siebert, besides the original works 
of nearly all the chemists mentioned for the past century and 
a half, have been consulted. It has not been thought neces- 
sary, in so brief a work as this, to give references to such 

literature, so they have been omitted. 

P. P. V. 
Chapel Hill, N.C., June, 189J. 




Derivation of Name. — Mysticism. — Manuscripts and Original Sources. — 
Destruction of Early Writings. — Chinese Sources. — Aryan. — Egyp- 
tian. — Chaldean. — Jewish. — Degree of Knowledge 1-7 


Hermes. — Inscription of Hermes. — Hermetic Philosophers. — Demok- 
ritos of Abdera. — The Greeks and Natural Science. — Mutability of 
Nature. — Theories of the Greek Philosophers.— Aristotle. — The Four- 
element Theory. — Greek Contributions to Science 7-12 


Zosimus the Panopolite. — Africanus the Syrian. — Synesius. — Olympi- 
odorus. — Breaking up of the Alexandrian School. — Transference of 
Learning to Arabia 12-15 


Apparatus. — Metallurgy. — Minerals and Salts. — Glass-making and 
Pottery. — Dyeing and Tanning. — Soaps, Medicaments, etc. . . 15-19 



Science in the East. — Science in Spain. — Progress made by the Ara- 
bians. — Geber. —His Writings. — Nature of his Work. — Views as to 
Sulphur and Arsenic. — Views as to Transmutation. — Apparatus. — 
New Substances known to Him. — Avicenna. — Other Arabic Chem- 
ists 20-25 


Characteristics of the Age. — Albertus Magnus. — Writings. — Work 
and Theories. — Thomas Aquinas. — Roger Bacon. — Writings and 
Work. — Discoveries. — Views as to Transmutation. — Arnold Villano- 
vanus. — Work and Writings. — Raymond Lully. — Character of his 
Work. — Growth in this Period 25-32 


Basil Valentine. — Work and Theories. — Writings 33-35 




Growth in the Belief in Transmutation. — Confirmations of the Belief. — 
Traditions as to Gold-making. — Theories as to the Origin of the Metals. 

— Legal Prosecution of the Gold-makers. — Mystical Language. — 
Sharpers and Charlatans. — Adepts. — Universal Medicine. — Other 
Aims of the Alchemists 35-40 



Paracelsus. — Character of his Work. — As a Physician. — As a Chem- 
ist. — Contributions to Pharmacy. — Extracts from his Writings. — His 
Followers. — Libavius. — Agricola 41-46 


Van Helmont. — His Theories. — Study of the Gases. — Views on 
Transmutation. — Ideas of Physiology. — Sennert. — Glauber. — Theory 
of Double Decomposition. — Suggestions for Industrial Improvements. 

— Sylvius. — Mistakes of the Iatro-chemists 46-50 


Phlogiston Theory. — General Characteristics. — Boyle. — Character of 
his Work. — Experiments upon Air. — Constitution of Matter. — 
Improvements in Qualitative Analysis. — Kunckel. — His Work. — 
Becher. — His Theories. — Homberg. — Lemery. — Stahl. — Character 
and Work. — Theory of Combustion. — General Chemical Work. — 
Hoffmann. — Boerhaave. — Overthrow of Alchemical Notions. — Writ- 
ings. —Other Phlogistics in Germany. — Phlogistics in France. — 
Macquer 50-62 


Hooke's Theory of Combustion. — Black. — Causticity of Lime and the 
Alkalies. — Latent Heat and other Work. — Cavendish. — Discovery of 
Hydrogen. — Analysis of the Atmosphere. — Priestley. — Invention of 
the Pneumatic Trough. — Emigration to America. — Character of his 
Work. — Discovery of Oxygen. — Relations of Plants and Animals to the 
Atmosphere. — Imperfect Analytical Work. — Views as to Combustion. 

— Other Researches 62-68 


Bergman. — Improvement in Analysis. — Views as to the Atmosphere. — 
Theoretical Views. — Scheele. — His Discoveries. — Discovery of Oxy- 
gen. — Theoretical Conclusions 68-72 



Lavoisier. — Character of his Work. — Experiments upon Combustion. 

— Composition of the Atmosphere. — Professional Character. — Compo- 
sition of Water.— Theory as to Aoids. — Transmutation of Water refuted. 


— Indestructibility of Matter. — Relation of Plants and Animals to the 
Atmosphere. — Nature of Heat. — Investigation of Organic Substances. 

— Chemical Nomenclature . 73-80 


Its Basis. — The Elements. — Spread of New Ideas 80-84 


Constancy of Proportions. — Berthollet. — Views of Affinity. — Dalton. 

— Atoms. — Proust. — Richter. — Law of Multiple Proportions. — The 
Atomic Theory and its Extensions 84-90 


Dalton's Rules. — Gay Lussac. — Law of Volumes. — Difficulties and 
Objections. — Avogadro's Theory. — Ampere. — "Wollaston's Equiva- 
lents. — Prout's Hypothesis 90-94 


Klaproth. — Proust. — Sir Humphry Davy. — Decompositions by Means 
of Electricity. — Decomposition of Water. — Decomposition of the Alka- 
lies. — Composition of Muriatic Acid and the Nature of Acids. — New 
Theory of Acids. — The Alkalizing Principle. — Davy's Later Life, 94-101 


Berzelius. — Character of his Work. — Analytical and Experimental 
Work. — Determination of the Atomic Weights. — Introduction of 
Symbols. — Dualistic Theory. — Electro-chemical Theory . . 101-107 


New Appliances. — The Laboratory of Berzelius. — Apparatus. — Law 
of Dulong and Petit. — Law of Mitsclierlich. — Corrected List of Atomic 
Weights. — Electro-chemical Equivalents. — Work of Dumas on Atomic 
Weights. — Vapor Densities. — Unsatisfactory Condition of Chemical 
Theory. — Gmelin's Views. — Need of New Support for the Atomic 
Theory 108-114 



Lavoisier's Views. — Organic Substances as the Product of Life Force.' 

— Views of Berzelius. — Theory of Compound Radicals. — Isomerism. — 
Synthesis of Urea. — Organic Analysis. — Classification of Organic Sub- 
stances. — ■ Extension of Electro-chemical and Radical Theories. — The 
Radical of Benzoic Acid. — Changes in the Radical Theory. — The Com- 
pound Radicals. — Atomic Theory Confirmed. — Overthrow of Dualism. 

— Substitution Theory. — Trichloracetic Acid. — Unitary Theory. — 
Nucleus Theory. — Type Theory. — Copulas and Conjugated Com- 
pounds. — Kolbe's Remodelling of the Radical Theory . . . 115-128 



Frcukland's Work upon the Organo-metallic Bodies. — Polybasic Acids 

— Atomicity of the Complex Radicals. — Introduction of the Idea of 
Valence. — Deduction of Valence from Inorganic Compounds. — Prog- 
ress made by the Valence Theory 128-131 


Discovery of New Elements. — The Halogen Acids. — Allotropism. — 
New Acids and Salts. — The Permanent Gases 131-133 


Graham's Work. — Diffusion Experiments. — Colloids and Crystalloids. 

— The Spectroscope. — Spectrum Analysis. — Polariscope and Micro- 
scope 133-137 


New Systems of Classification. — Atomic Chains. — Physical Isomerism 
and Stereo-chemistry. — Atomic Linkage .... ... 137-139 


Confusion in the Sixth Decade. — Dumas' Revision of the Atomic 
Weights. — The Work of Stas. — Continued Confusion of Standards. — 
Cannizzaro's Revision. — Numerical Relations between the Atomic 
Weights. — Newland's Law of Octaves. — Mendeleeff 's Periodic Law. 

— Importance of the Law. — Primal Elements 140-144 




Followers of Berzelius. — Work of Fresenius. — Associated Methods. 



The Humus Theory. — The New Theory of Liebig. — Field Trials. — 
Other Investigators. — Experiment Stations 148-151 


The Problems to be solved. — Condition of the Scienoe. — Fermentation 
and Decay Processes. — Discovery of the Nature of Ferments . 151-153 


Molecular Weight Determinations. — Determination by means of Freez- 
ing-Points and Boiling- Points. — Electro-chemistry. — Electro-chemical 
Analysis. — Electro-metallurgy. — Thermo-chemistry. — Photo-chemis- 
try. — Early photo-chemical Observations 153-157 





In attempting to discover traces of a science in earliest 
historic times, one must first disabuse his mind of the idea 
that he will find it in anything like the elaborated modern 
form in which he knows it. These natural sciences are the 
result of a long process of evolution, and the primal form 
will probably prove a very much disguised one. In most 
cases it is idle to speak of systematic science as existing 
among the ancients. Unquestionably there was knowledge 
of isolated scientific facts, — here and there one may find a 
crude theory, more justly to be styled a philosopher's dream, 
— but of system there was none. 

When one speaks, then, of the birth of chemistry, some 
such stage is meant as that of the ovum, which will lead 
through a series of metamorphoses up to the perfected insect. 
And yet it is most useful and entertaining to study these 
transformations. Rodwell aptly compares it to the study of 
the history of a nation. There is first the groping after 
causes, and then the struggle to frame laws. There are in- 
tellectual revolutions, bitter controversial conflicts, and the 
crash and wreck of fallen philosophies. As it is important 



to study the history of some people's growth, so we should 
follow the lines of march and onward progress of a great 
science. We know far too little of the struggles and war- 
fare, the privations and sacrifices, the heroes and princes 
who have striven and wrought for us, and by whose labors 
our burdens are lightened, our comforts increased, and our 
minds enlarged. 

Derivation of the Name. — The ovum from which chemistry 
has been slowly evolved seems to have been sorcery and 
magic. The name itself is most plausibly explained as point- 
ing to this. The word xw- £ta occurs first in the writings of 
Suidas, a Greek lexicographer of the eleventh century. It 
is there defined as the " preparing of gold and silver." This 
is manifestly a Greek rendering of the name Chema or Chemi, 
which is of Egyptian origin, and all attempts at deriving it 
from yiu>, to fuse, or xv/iui, a liquid, are without import. 
Plutarch tells us that Chemia was a name given Egypt on 
account of the black soil, and that this term further meant 
the black of the eye, symbolizing that which was obscure and 
hidden. The Coptic word khems or chems is closely related 
to this, and also signifies obscure, occult, and with this is 
connected the Arabic word chema, to hide. It is therefore 
the occult or hidden science, the black art. Zosimus, the 
Panopolite, says that the giants, sprung from the union of 
the angels and the daughters of men, were taught all that 
was supernatural and magical by their fathers, and this won- 
derful knowledge was recorded in a book called Chema. 

Mysticism. — Two difficulties meet one in studying the 
early history of the science. One is just such mysticism as 
is seen in the quotation made from Zosimus, and the other 
is the custom among the early writers of ascribing their dis- 
coveries, books, etc., to fabulous names or ancient heroes and 


gods. This latter had two objects, the first being to shield 
the true author in time of persecution, and the second to gain 
a certain amount of credit and reputation for a discredited 
art by the use of the names of such celebrities as Moses, 
Solomon, Alexander, or Cleopatra. This tendency is espe- 
cially noticeable among the writers of the Middle Ages, and 
also the early Greek authors, and is not peculiar to authors 
of alchemical treatises. 

Manuscripts and Original Sources No original manuscript 

of the earliest writers on chemistry or alchemy has been dis- 
covered. Our knowledge must be gleaned from the pages of 
those writing upon other subjects, or must come from frag- 
ments handed down to us through several copyists. The 
earliest manuscripts that are known are preserved in the 
museum at Leyden, and were found at Thebes, probably in a 
tomb, enclosed -in the wrappings of a mummy. They are of 
the greatest possible interest to chemists, and have been most 
carefully studied and commented upon by Berthelot. They 
are written partly in the Greek and partly in the Demotic 
character, though they are known as the Greek papyri. The 
earliest is somewhat fragmentary, the beginning and the end 
being lost. It was written apparently about the third cen- 
tury of the Christian era, and belonged to the class of books 
burned by Diocletian. These manuscripts are filled with 
magical formulas, recipes, and descriptions of chemical pro- 
cesses, together with drawings of various forms of apparatus. 
Eodwell states that there is said to be a Greek manuscript of 
the fifth century in the King's library at Paris, and others 
of a somewhat later date in the libraries of Munich, Milan, 
Venice, Hamburg, and Madrid ; but he is inclined to doubt 
whether any of these were written before the ninth or tenth 
century. They are probably the work of monks living at 
Alexandria and Constantinople. 


Destruction of Early Writings. — The reason generally- 
assigned for this absence of early records is that Diocletian 
burned all writings of the Egyptians bearing upon alchemy, 
because, as he said, these taught the art of making gold and 
silver; and, by destroying them, he took away from the 
Egyptians the power of enriching themselves and rebelling 
against the Romans. Whether Diocletian actually ordered 
the books to be burned or not, it is certain that these books 
of a feared and prohibited art were subject to many another 
foray, as is evidenced by the scene recorded for us in the 
Acts of the Apostles : " Many of them also which used curious 
arts brought their books together and burned them before all 
men ; and they counted the price of them, and found it fifty 
thousand pieces of silver." Such scenes were often repeated 
in the early part of the Christian era, and Diocletian had 
only to complete these iconoclastic ravages. 

Chinese Sources No Chinese nor Japanese writings of 

early date on chemistry are known, with certainty, to exist. 
Some have been reported, but they appear untranslatable and 
their contents are unknown. Where the early literature is so 
imperfectly known, it is impossible to trace, on the part of 
these people, the growth of their knowledge of chemical sub- 
stances and forms of combination. It is certain that the 
Chinese have had some knowledge of metals, alloys, colors, 
and salts for a long time, and that they manufactured gun- 
powder and porcelain before they were known in Europe. 

Aryan Sources. — In the same way, with regard to the 
Aryan races of India, we can only say that their knowledge 
of the extraction of metals, the making of steel, the prepara- 
tion of colors, and similar technical operations, dates back to 
the most remote antiquity. They also theorized as to the 
elements and their number. Their synonym for death was, 


"man returns to the five elements." Magic and mysticism 
find their natural home in India to the present day. 

Egyptian Sources. — The almost universal tradition among 
alchemists is that their art was first cultivated among the 
Egyptians, and that Hermes Trismegistus, the Egyptian god 
of arts and sciences, was its founder. The finding of papyri 
of a chemical nature in the tombs, and many other facts, lead 
us to give credence to this tradition so far as the early culti- 
vation of the art among the Egyptians is concerned. Clement 
of Alexandria tells us that the knowledge of this occult science 
was restricted to the priests, who were forbidden to commu- 
nicate it to any save the heir-apparent to the throne, and to 
such among them as excelled in virtue or in wisdom. Plutarch 
also mentions the strict secrecy observed, and the cloaking of 
their knowledge under the guise of fables. The art was es- 
pecially cultivated in the great temple at Memphis. Ptah-mer, 
the high priest of Memphis, whose statue is preserved in the 
Louvre, was so great an adept that he was said to know all 
things, and yet could conceal this knowledge from others as 
with a veil. The searching out of the books of the Egyptians 
and their burning by the Roman Emperor is another proof of 
the early and wide-spread practice of this art among them. 

Further, there is a similarity easily detected between the 
hieroglyphics and the alchemical signs. The phraseology in 
the early treatises is similar to that in the priestly writings. 
Lastly, we must note the important part' played by the num- 
ber four with the alchemists as well as with the Egyptian 
priests. There are the four bases or elements, the tetrasomy 
of Zosimus ; the four zones, four funeral deities, four cardinal 
points, four winds, four colors, etc. 

Chaldean Sources. — The Chaldeans, as masters of occult 
sciences, played an important part at Rome. In much earlier 


times, the Bible mentions them as the depositaries of all wis- 
dom and science, the trusted advisers of the far Eastern kings. 
They were rivals of the Egyptians in knowledge, and were 
especially famous as astrologers. Many industrial arts were 
brought to as high perfection in Babylon as in Egypt ; for 
instance, the processes of glass-making, of dyeing, and of 
working in metals. Those Chaldeans who settled in Rome in 
later years came from Syria and Mesopotamia. Tacitus 
makes mention of them. They were much sought after by 
the fashionable as the representatives of Eastern religions and 
mystic doctrines. Ostanes, the Mede, was one of the celebrated 
early alchemists. Several writers have recorded for us the 
existence of a book called " The Book of the Divine Prescrip- 
tions," which seems to have been the most famous writing of 
these Persian sages. 

The belief in some wonderful connection between planets 
and metals is due to these Chaldeans. The signs of the 
heavenly bodies became the symbols for the metals. These 
planets influenced a supposed growth of the metals, and were 
esteemed all-powerful in regulating human life and fate. 
Many of these notions are to be attributed to the Alexandrian 
epoch. The idea of the macrocosm, or outer world, and the 
microcosm, or little inner world of a man's own nature, which 
is so often referred to and utilized in alchemical writings, 
originated also at Babylon. 

Jewish Sources In many of the treatises on alchemy we 

meet with Jewish names, and some of these writings have 
been ascribed to Jewish authors. Though jealous guardians 
of the only pure religion, the Jews sought after other gods. 
They were often superstitious, and believers in magic and 
demons. They were very learned ; and at Alexandria, where 
Greek culture came in contact with the culture of Egypt and 
of the Chaldeans, the Jews, for a while, just at the time of the 


birth of Christianity, were at the head of science and philos- 
ophy, and played a very important part in the fusion of Greek 
doctrines, scientific and religious, with those of the Orient. 

The European nations first became interested in the occult 
science in times much later than those we have been referring 
to in connection with the Eastern nations. 

Degree of Knowledge. — As to the degree of knowledge 
attained, apart from mysticism and magic, we find that the 
practical and useful came first before all theory. A somewhat 
detailed account of this knowledge will be given later. There 
is much to prove that, both at Babylon and in Egypt, the 
industrial arts were practised with a high degree of skill ; but, 
of course, all was empirical, and hence very slow of develop- 
ment. There is little evidence of any attempt at finding out 
the causes of the changes observed or brought about. 


Hermes First among the names connected with alchemy 

before the Christian era is that of Hermes Trismegistus. He 
is by some supposed to be identical with Canaan, the son of 
Ham. The name is synonymous with Toth, the god of intel- 
lect, the patron of arts and sciences in ancient Egypt. The 
adepts in alchemy were unanimous in writing of him as the 
founder of their art. He was said to be the author of twenty 
thousand or thirty-six thousand five hundred books, which 
means probably that, as the god of letters, all books were 
dedicated to him and he was in one sense their author. Clem- 
ent of Alexandria describes the solemn procession in which 
these books were borne in the great ceremonies. Tin and 
mercury were set apart as metals sacred to him. During the 
Middle Ages the science was often known under the name of 
the Hermetic Art. 


Inscription of Hermes Albertus Magnus, in a treatise at- 
tributed to him, tells us that Alexander the Great found in 
the sepulchre of Hermes (or in the tomb of Sarah) certain 
emerald tables inscribed with the secrets of his wisdom. This 
famous inscription is constantly quoted in books on alchemy. 
It consisted of thirteen parts or sayings. They are sufficiently 
obscure to receive almost any interpretation. The most care- 
ful commentators agree that they refer to the universal medi- 
cine or the philosopher's stone. Two quotations will suffice 
to give an idea of the whole. 

No. 7. Separate the whole earth from the fire, the subtle 
from the gross, acting prudently and with judgment. 

No. 8. Ascend with the greatest sagacity from the earth 
to heaven, and then again descend to the earth, and unite to- 
gether the powers of things superior and things inferior. 
Thus you will possess the glory of the whole world, and all 
obscurity will fly far from you. 

To most this seems a meaningless forgery of the early 
alchemists. Still, this mystical personage had great influence 
and through many centuries. We find various axioms as- 
cribed to Hermes, also a mystic hymn, and a so-called instru- 
ment or table of figures for predicting the outcome of disease, 
a life's fate, etc. Such tables were used in very ancient times 
in Egypt. 

The Hermetic Philosophers The alchemists called them- 
selves the Hermetic Philosophers, and followed the Hermetic 
Art or Hermetics. To close anything very securely, as, for in- 
stance, to seal it in a glass tube, is called to this day sealing it 
hermetically. In old times the symbol of Hermes was affixed 
to the article, and it was thus sealed with " Hermes, his seal." 

Demokritos of Abdera The earliest historical personage 

connected with alchemy is Demokritos of Abdera, who lived 


460-357 b.c. He was the founder of the atomistic school, ex- 
tending and developing the theory of Leukippos. His defi- 
nition of the atom is almost as absolute and precise as that / 
found in modern treatises. His chieT work was entitled 
" Physica et Mystica." Aristotle frequently cites from the 
writings of Demokritos. Many works have been ascribed to 
him which were undoubtedly the productions of later centu- ■ 
ries. As was customary for men of learning in early times, 
Demokritos visited Egypt, Chaldea, and various parts of the 
East, in the search of knowledge, and doubtless owes much to 
the wise men of those regions. 

The works of Demokritos and his school formed a sort of 
encyclopaedia of philosophy and science. These books are 
unfortunately lost, with the exception of a few fragments. 
Pliny tells us that Demokritos was instructed in magic by 
Ostanes the Mede. The name of Demokritos is found in the 
Leyden Papyrus, in the magic ritual there recorded. To him 
was attributed also a table called the Sphere of Demokritos, 
for foretelling death or recovery from a malady. This was 
similar to the table of Hermes mentioned above. It is impos- 
sible to tell how much of the magical and alchemical should 
justly be accredited to this Greek philosopher. 

The Greeks and Natural Science The observation and ex- 
periments necessary for the pursuit of alchemy did not com- 
port with the Greek idea of philosophy. This is shown by 
the saying of Socrates, that the nature of external objects 
could be discovered by thought without observation, and by 
the renunciation of all natural sciences by the Cynics. This 
came largely from the fact that they saw in the nature around 
them the mutable only. Plato separated logic, as the knowl- 
edge of the immutable, from physics, the knowledge of the 
mutable. That which was subject to indefinite change would 
not repay observing nor recording, therefore they could not 


conceive of astronomy and physics as serious objects of mental 
occupation. There was nothing to be learned from fields and 
trees and stones. One of the philosophers is said to have 
gone to the length of putting out his eyes, in order that his 
mind might not be influenced by external objects, but might 
wholly give itself to pure contemplation. The intellectual 
power and grasp of these philosophers were wonderful, but 
faulty and misleading, since the real and practical was left out. 

The Mutability of Nature as viewed by the Ancients. — The 
Egyptians and other ancient peoples held the same idea of 
the mutability of all external objects, and the absence of law 
in their changes. They could see no regularity, no laws, 
governing their changes, and looked for none. With the 
observing faculty thus blunted, progress in science was neces- 
sarily slow. The investigation of nature was even considered 
impious. The phenomena of nature were brought about by 
the gods, and their actions should not be inquired into too 
closely by men. This manner of thinking is not yet extinct. 

Theories of the Greek Philosophers. — The theories of the 
early Greek philosophers, then, were not based upon close 
observation and a multitude of facts experimentally learned, 
as all modern theories are. " The baseless fabric of a vision " 
more nearly describes them. Rodwell gives a most interest- 
ing resume of the theories of these philosophers with regard 
to the formation of the world and the primal elements. These 
elements were not the chemical elements of the present day, 
but rather principles. They meant more the characteristic 
and essential properties of matter than matter itself. Thales 
of Miletus (sixth century B.C.), the " first of the natural phi- 
losophers," affirmed that water was the first principle of all 
things. This theory had its supporters even during the 
Middle Ages, philosophers who got water from air and solids 


by evaporating water, and carefully proved that plants would 
grow when fed with water only. The theory was not com- 
pletely disproved until a little more than a century ago. 

Anaximenes regarded air as the primal element; Herak- 
leitos, fire ; Pherekides, earth. According to Anaximenes, 
clouds are caused by the condensation of air, and rain by the 
condensation of clouds. Archelaus said that air, when rare- 
fied, became fire ; when condensed, water ; and water, when 
boiled, became air. 

Empedokles introduced the idea of four distinct elements, 
— earth, air, fire, and water, — which were not interchangeable, 
but formed all things by mixing. Anaxagoras of Klazomene 
(500 b.c.) seems to have been the first of the Greeks to form- 
ulate a theory approaching the atomic. This was more clearly 
expressed by Leukippos and extended by Demokritos. Long 
before the time of any of these, however, the idea seems to 
have been conceived in India. 

Aristotle. — Aristotle was the most prolific writer on 
science among the ancients. His books have come down to 
us, and have exerted a wonderful influence over all fields of 
knowledge. Yet there was nothing bearing directly upon 
chemistry in his writings, nor do we find a single one among 
the learned men of ancient Greece who can be looked upon as 
aiding directly in the advancement of chemistry, except De- 
mokritos. The views of Aristotle on science, metaphysics, and 
ethics were almost universally accepted during the Middle 
Ages, and held undisputed sway for nearly twenty centuries. 
He introduced into the science many new ideas, as, for in- 
stance, a fifth element, the quinta essentia, which he called 
ether more subtle and divine than the other elements. From 
this comes the word quintessence, so much used by the 
alchemists, and used in a different sense now. We have to 
assume the existence of a rarefied ether in the theories of 
the present day. 


The Four-element Theory Aristotle added much to the 

theory of the four elements, assigning properties to each, and 
elaborating the changes caused by their mingling, and also 
dwelling on their inter-convertibility. This was often cited as 
justifying the idea of the transmutation of the metals. The 
four elements — earth, air, fire, and water — became known as 
the Aristotelian elements, and from them various names were 
derived in the early chemical books. Thus there were earths, 
alkaline earths, rare earths, etc. ; fixed airs, inflammable airs, 
dephlogisticated air, and others; and a number of different 
waters, — aqua fortis, aqua regia, aqua ammonia, etc. 

Greek Contributions to the Science The absence of actual 

experiment, the philosophical sophistries, and the decrying of 
all observation of nature as useless speculation, render the 
intellectual work of the Greeks of small value in science. 
Yet they had more or less definite notions as to matter and 
force. The four-element theory, the atomic theory, the idea 
of an ethereal medium, of the transmutation of metals, of 
changing one form of matter into another by some active 
energy or principles — these are mostly distinct gains in 
scientific thought. The motive principle causing combination 
and change was, in the philosophy of Anaxagoras. the i/ovs ; in 
that of Demokritos, ava.yK.ri; of Herakleitos, fire; of Aristotle, 
the moving ether. In our day we call it affinity, but we are 
still a long way off from solving the mystery of its nature. 


In the period from the dawn of Christianity to the fifth 
century we have the Greek school predominating. For the 
first time we come across historic personages from whom 
authentic writings have been transmitted to us. These were 
genuine alchemists. In this period alchemy attained con- 


siderable notoriety, and was of sufficient interest and im- 
portance to be celebrated by the poets. Bishops, embassadors, 
physicians, philosophers, were engaged in the pursuit of the 
science, and have left us fragments of their works. 

Zosimus, the Panopolite — First among these is Zosimus, 
the Panopolite. He is the most ancient of the alchemists 
whose works we possess. He lived in the third century of 
the Christian era; and Suidas, the Greek lexicographer, tells 
us that he wrote twenty-eight books on alchemy entitled 
" Manipulations?' Most of these books are lost. Still, many 
of his treatises have been collected from the Greek papyri ; 
and, though often obscure, they give us a good idea of the 
learning of the man and of his times. They contain descrip- 
tions of apparatus, of furnaces, studies of minerals, of alloys, 
of glass-making, of mineral waters, and much that is mys- 
tical, besides a good deal referring to the transmutation of 
metals. How much of these fragments is properly to be 
ascribed to him it is impossible to say. He is cited as the 
author of the saying that like begets like, and is often quoted 
by the alchemists of later times, being always spoken of with 
deep respect as a great and learned master of the science. 

Africanus, the Syrian Africanus, another of these alche- 
mists, was a Syrian of the time of Heliogabalus. He is said 
to have written on medical, agricultural, and chemical sub- 
jects. Certain geographical and military works are also 
attributed to him. 

Synesius Synesius is an important name in the history 

of the fourth century. He was named Bishop of Ptolemais, 
and was an astronomer, physician, agriculturist, and embas- 
sador. His works were published in 1631 in Paris. They 
are mostly philosophical and commentaries on Zosimus. 


Olympiodorus — Olympiodorus is more noted as a his- 
torian. He was a native of Thebes, and wrote a history of 
his times. He was not so obscure in his language as Zosi- 
mus. He reproduced the early Greek philosophy of Thales 
and Anaximenes. He seems to have been the first to divide 
matter into the fixed and the volatile, a distinction depending 
upon the combustibility. 

These few names serve to give some idea of the character 
of the Greek alchemists. It is impossible to speak of the 
progress made by, or the learning of, each one. 

Breaking up of the Alexandrian School — Alexandria had 
been, during this period, the centre of science and philos- 
ophy. Under Roman rule and depreciations it gradually 
declined, until by the fourth century no buildings of impor- 
tance were left in it except the Temple of Serapis. This was 
the great bulwark of Greek culture and of medical and al- 
chemical study. Under an order to destroy all heathen tem- 
ples, this also was destroyed in the reign of Theodosius, and 
most of the books in the magnificent library suffered the 
same fate. The Serapeum of Memphis and the Temple of 
Ptah, where the medical laboratories and the workshops of 
the alchemists were probably to be found, were destroyed at 
the same time. And thus the learned men of Greece and 
Egypt were dispersed, suffering a political and a religious 

Transference of Learning to Arabia The light of science 

was transferred to Constantinople, communicated in the sixth 
and seventh centuries to the Arabians, and by them in turn 
to their brothers of Mesopotamia and Spain. The name al- 
chemy, al-embic, al-cohol, etc., are of Greek origin, with the 
Arabic article prefixed ; and they point to the source of the 
knowledge possessed by the Arabians when Europe was in 


darkness. This darkness which came over Europe is to be 
accounted for by the many political changes which took place 
in the Western Empire. Revolutions and invasions were 
frequent, and the capital had to be moved from place to 
place. There was a general breaking up of the loosely jointed 
empire, and a foundation of strong priestly orders hostile to 
all independence of thought. 


Although chemistry as a science was unknown to the an- 
cients, they possessed some knowledge of chemical substances, 
and were by no means ignorant of various manufactures and 
industries based on chemical processes ; and hence they had a 
sort of practical or technical chemistry. In certain branches 
of metallurgy, in glass-making, dyeing, and tanning, they 
attained decided proficiency. 

Apparatus — First, as to the apparatus used in the work- 
shops, we derive some information from the Greek papyri. 
These contain many drawings of alembics and other forms 
of apparatus, which may of course have been the discovery of 
later workers if the great age of these papyri is denied. The 
processes used were those requiring the aid of fire ; crucibles, 
furnaces, etc., therefore abound. Mention has already been 
made of the treatise of Zosimus, " On Instruments and Fur- 
naces," in which he claims to describe the various appliances 
he saw in the temple at Memphis. These different forms of 
apparatus were made of gold or bronze or clay-ware. The 
alembic was a crude form of distilling apparatus, and comes 
from the Alexandrian period. The water-bath, or bain-marie 
as it is still called by the French, was said to have been in- 
vented by Mary the Jewess at a very early period. The 
blow-pipe and bellows are both figured among these drawings, 
as well as on very early Egyptian and other monuments. 


Metallurgy Six metals were well known, — gold, silver, 

tin, iron, copper, and lead. Homer mentions these six, and the 
Bible does also ; so they seem to have been in use from a very- 
early antiquity. Mercury was afterwards added to the list. 
The derivation of the word metal is from the Greek word 
fitraXXdu), " to search after," and the noun first meant or 
referred to mines. The ancients, especially the Egyptians, 
were very skilful workers in metals. They made gold wire 
and leaf, and fine inlaid work, and very beautiful ornaments. 
Gold was the first known of the metals apparently. Its 
color, lustre, and malleability attracted the attention of the 
early peoples. Its occurrence free in nature and in a bright 
pure state would doubtless account for its being utilized first 
of the metals. Early vessels were made of it ; and it was 
used for coating, or plating, over wood and other materials. 

Silver seems to have been known at very nearly the same 
time as gold. It also occurs free, and was easily j>repared 
ready for use. Then follow copper, iron, tin, and lead. 
The Egyptians attributed the discovery of these metals to 
their sovereigns ; the Phoenicians and other nations, to their 

The purification of gold and silver by the cupellation 
process was known before the Christian era, but there was no 
means of separating gold from silver. The alloy of the two 
metals, as they are often found together in nature, was re- 
garded as a peculiar metal itself, and was called electrum. 
The oldest coins we have are made of this electron, or pale 
gold. This alloy was made artificially out of three parts of 
gold and one of silver. 

Copper was in use before iron, and was called ^aXxds by 
Homer. From this we get the word chalcopyrite and others. 
The Romans got it first from the Island of Cyprus, and called 
it aes cyprium ; and from this it became cuprum,, and in Eng- 
lish copper. It was used mainly in alloys. Aurkhalcum, or 


golden copper, they called the alloy made from copper and an 
ore of zinc ; and this is known now as brass. They were igno- 
rant of the metal zinc in the free state. Bronze was an alloy 
of copper and tin, and was known also before metallic tin. 
This was very strong, and much easier to work into shape 
than iron, and hence was a substitute for it. Weapons and 
many utensils were made from it. Iron was known in very 
early times ; Lepsius maintaining that the Egyptians used it 
five thousand years ago in the preparation of the harder in- 
struments which they required for much of their work, as in 
building the pyramids, and engraving precious stones. Iron 
was coined by the Greeks, and in the time of Homer they 
used it for axes and ploughshares. As it rusts so easily 
very few early implements have come down to us. The early 
Egyptians understood how to harden or temper iron. Steel 
was made in India at a very early period. The difficulty of 
reducing iron from its ores, and the fact that it does not occur 
free, would account for its not being used more largely and 
at an earlier time. 

Tin was obtained from India and Spain and afterwards 
from Britain. It was one of the articles of commerce used in 
trade by the Phoenicians. Mirrors were made of it, and cop- 
per vessels were coated over with it. Lead and tin seem to 
have been regarded as varieties of the same metal, and were 
called plumbum nigrum and plumbum candidum. Pliny 
speaks of conveying water in leaden pipes, and Homer makes 
much earlier mention of the metal. It came mainly from 
Britain and Spain; and from this latter country mercury was 
also gotten, and was used, as now, in extracting gold from its 
ores. The first mention of it was in 300 b.c. Native mer- 
cury was called argentum vivum (quicksilver), and mercury 
distilled from cinnabar was known as hydrargyrum (v8a>p, 
apyvpos). Various compounds of these metals were known and 


Minerals and Salts The two oxides of copper were used in 

glass-making ; verdigris was manufactured and put to several 
uses; white lead was used as a cosmetic by the Athenian 
ladies, and found further use as a medicine; red lead was used 
as a paint; stibium, or native antimony sulphide, was used as 
a paint for the eyelashes, and is still used for that purpose in 
the East under the name of kohl ; black oxide of manganese 
was used in glass-making, especially for clearing up darkened 
masses, and so got its name of pyrolusite; the native car- 
bonate of zinc was also known and used ; the sulphides of 
arsenic, orpiment and realgar, were well-known pigments. 
According to Sir Humphry Davy, the ancient Greeks and 
Eomans had almost the same colors as those employed by 
the great Italian masters at the period of the revival of arts 
in Italy. 

Soda and potash were both used in washing and whitening 
clothes, in glass-making, and in saponifying the fats for 
soap and unguents. Lime was burned and mortar made 
from it, though the earliest cementing material was bitumen. 
Bitumen and asphalt were also used for torches and em- 

Glass-making and Pottery The art of glass-making is ex- 
ceedingly old, and apparently originated with the Egyptians. 
They reached a high degree of proficiency in its preparation, 
knowing how to color it, and also how to prepare imitation 
precious stones from it. Clear, transparent, colorless glass 
was not known by them, however. 

They were also skilful in the production of clay-wares 
and pottery. The Egyptians decorated these wares with col- 
ored enamels. The Etruscans showed great skill in the 
ceramic art. From the earliest ruins have been unearthed 
specimens of pottery. The Chinese, alone of early nations, 
knew how to make porcelain. 


Dyeing and Tanning — Dyeing was carried to great perfec- 
tion. Many vegetable and animal coloring matters were 
known. Mordants were used, and the effects produced were 
very beautiful. Paints were also prepared, and applied with 
brushes. The following mineral colors were known at the 
time of Pliny : white lead, cinnabar, litharge, smalt, verdigris, 
ochre, lampblack, realgar, orpiment, and stibnite. 

Leather was tanned, at first by means of oil, and later with 
bark, very much after the manner in use now. The hair was 
removed by means of lime, as is still done. Some leather, 
said to have been tanned at the time of Solomon, has been 
found in modern times fairly well preserved. 

Soaps, Medicaments, etc — Soap was made by mixing wood 
ashes with animal fats, thus saponifying them. It was used 
as a kind of pomatum ; unguents, oils, etc., were rubbed upon 
the body in the place of soap as used in modern times. Both 
hard and soft soap were known. Burnt lime was often added 
in the manufacture. 

Many substances were used as medicaments ; some of these 
might be called chemical preparations, showing an early union 
between chemistry and pharmacy. Lead plasters were made 
from litharge and oil, iron rust was used, also alum, soda, and 
bluestone. The use of sulphur as a disinfectant is mentioned 
in the well-known passage in Homer, in which he speaks of \j 
its being burnt to drive away the evil spirits from a home. 
It was also used for bleaching purposes. The only acid known 
was acetic acid, or vinegar ; and its solvent power seems to 
have been greatly over-estimated. 




Science in the East Greek learning, with its rudimentary 

science, had been transferred to Arabia and Persia. The 
decline and fall of the Eoman. Empire had left Europe in 
intellectual darkness ; on the other hand, universities, 
libraries, museums, and observatories were founded and 
maintained by the Arabians. About the middle of the eighth 
century the caliph Al-Mansour (754-775) founded the city of 
Bagdad. He was all-powerful, his land was blessed with 
peace, and he began to cultivate the arts and sciences. He 
founded an academy or university at Bagdad, which became 
very celebrated. Pupils and professors nocked to it from all 
quarters, and they numbered at one time as many as six 
thousand. Hospitals and laboratories were erected, and ex- 
perimental science began to be properly recognized. The 
names of several caliphs are connected with this university as 
its fostering patrons, for the successors of Al-Mansour contin- 
ued his work. Ancient books were collected, and every scrap 
that could add to their store of learning was eagerly saved. 
For several centuries this great institution of learning 

Science in Spain This love for learning extended to the 

western possessions of the Arabs. At Fez and Morocco 
academies were founded, but Spain was still more favored. 



The caliphate of Cordova was probably the most prosperous 
and splendid of the Moorish possessions, and the University 
of Cordova became the most celebrated in the world. It was 
attended by Christian students from all Western Europe, as 
well as by Moors. Its library contained two hundred and 
eighty thousand volumes, the catalogue filling forty-four vol- 
umes. The university produced one hundred and fifty authors. 
Other universities and libraries were scattered through Spain 
during this, its golden age. 

Progress made by the Arabians Yet with all their zeal for 

learning, and for hoarding old books, and their much writing 
of new ones, the Arabs made little progress in science. Cen- 
turies passed with but slight additions to what was already 
known. The greatest obstacle to the progress of science lay 
in their religion, though fortunately chemistry was the branch 
of science least obnoxious to their prejudices. Islamism pro- 
hibited magic and all arts of divination, and also all dissection 
of the human body after death. In the hands of the Arabians, 
therefore, alchemy was chiefly applied to the preparation of 
medicines. During this period there were two especially 
famous authors and workers, Geber and Avicenna. 

Geber Geber (eighth century) was a Sabean of Mesopo- 
tamia, of Greek parentage, but a convert to Islam. His name 
in full was Abou-Moussah-Dschafer-al-Sofi. Very little is 
known of his early history, though he may be looked upon as 
the founder of experimental chemistry, and was called the 
Father of Chemistry. Berthelot has shown that the existence 
of Geber is open to question, and his writings may be attrib- 
uted to a later date. 

His Writings. — Several manuscripts are to be found in the 
libraries of Europe, purporting to contain his writings. From 
what source he derived his knowledge we do not know, as he 


makes no mention of earlier writers except in a general way, 
speaking of the "ancients." Some think that he obtained 
his knowledge from Egyptian sources. His works were trans- 
lated into Latin in 1529, and into English in 1678. There 
are four treatises : 1. " Of 'the Search for Perfection ;" 2. "Of 
the Sum of Perfection ; " 3. " Of the Invention of Verity ; " 
4. " Of Furnaces." 

He makes no distinction in these between the knowledge 
gotten from others and that learned by his own experiments. 
His language is plain enough for one to understand most of 
the operations indicated and the substances named. 

The Nature of his Work. — The object of his work seems to 
have been the discovery of the philosopher's stone, by which 
he may have meant some great medicine or remedial agent. 
This interpretation is a matter of question, however. He 
was especially interested in finding out the properties of sub- 
stances, and experimenting upon the possibility of putting 
them to use as medicines. In his works we find various 
additions, made by himself or others, to the chemical knowl- 
edge already described as possessed by the ancients. 

He considered all metals as compounds of mercury and 
sulphur in varying proportions, an opinion which he says he 
derived from the ancients, and which was handed down with 
many variations through the Middle Ages. Gold and silver 
were the perfect metals, the others imperfect. He frequently 
made use of sulphur, and knew many of its properties. Geber 
writes thus of sulphur : — 

His Vieivs as to Sulphur and Arsenic. — " Sulphur is a sub- 
stance, homogeneous, and of a very strong composition. Al- 
though it is a fatty substance, it is not possible to distil its 
oil from it. It is lost on calcining. It is volatile, like a 
spirit. Every metal calcined with sulphur augments its 
weight in a palpable manner. All the metals can be com- 
bined with this body except gold, which combines with it 


with difficulty. Mercury produces with sulphur, by way of 
sublimation, Uzufur or cinnabar. Sulphur generally blackens 
the metals. It does not change mercury into gold nor into 
silver, as has been imagined by some philosophers." 

As to arsenic, he says : " Arsenic is composed of a subtile 
matter, and of a nature analogous to that of sulphur. It is 
fixed by the metals as sulphur ; and one prepares it, like the 
last, by the calcination of minerals." 

Views as to Transmutation. — His description of the metals 
is fairly accurate. As a proof of the possibility of transmu- 
tation, he gives an example of copper being changed into gold. 
" In copper mines we see a certain water which flows out and 
carries with it thin scales of copper, which (by a continued 
and long-continued course) it washes and cleanses. But after 
such water ceases to flow, we find these thin scales with the 
dry sand, in three years' time to be digested with the heat of 
the sun ; and among these scales the purest gold is found ; 
therefore we judge those scales were cleansed by the benefit 
of the water, but were equally digested by the heat of 
the sun, in the dryness of the sand, and so brought to 
equality." Very plausible reasoning from defective premises, 
as Thomson observes. 

Apparatus, etc. — In the treatise on furnaces he describes 
a furnace for calcining metals, and also gives a description 
of a furnace for distilling. In this there is a detailed account 
of the glass or stone ware or metallic aludel and alembic used 
in the process. He describes the distillation of many bodies, 
and uses the term spirit for volatile bodies in general ; thus 
mercury was a spirit. He made use of crucibles and cupels, 
and gives a full account of the purification of gold and silver 
by cupellation. He understood the purification of bodies by 
crystallization, solution, and filtration, calling the latter pro- 
cess distillation through a filter.- The majority of the chem- 
ical processes in use up to the eighteenth century were known 
to Geber. 


New Substances known to Him. — The alkaline carbonates 
were known to him, and he prepared caustic soda. He knew 
also saltpetre and sal ammoniac, and evidently made use of 
the mineral acids, nitric, sulphuric, and aqua regia. He made 
use of these as solvents, and thus the wet processes of modern 
chemistry began to substitute the furnaces of the old. Vari- 
ous vitriols or sulphates were spoken of by him, and also 
borax and purified common salt. Certain compounds of mer- 
cury were prepared by him ; among others, the chloride or 
corrosive sublimate and the red oxide. As an illustration 
of these processes we may take his method of preparing 
silver nitrate, which he discovered. 

" Dissolve silver calcined in solutive water (nitric acid), 
as before ; which being done, coct it in a phial with a long 
neck, the orifice of which must be left unstopped, for one 
day only, until a third part of the water be consumed. This 
being effected, set it with its vessel in a cold place, and then 
it is converted into small fusible stones, like crystal." 

His philosophy was not very advanced, as he ascribed the 
various phenomena he observed to occult causes. His writ- 
ings along this line are obscure and often unintelligible. 

Avicenna (078-1036) Avicenna was the next great Ara- 
bian scientist, exerting the same influence over medicine that 
Geber did over chemistry. He was called the Prince of 
Physicians, and as an authority ranked next to Aristotle and 
Galen. He was very precocious as a youth, repeating the 
Koran by heart at the age of ten. At sixteen he was a 
physician of eminence, and from that time on his career was 
one of great success, and yet marked by great dissipation. 
He was the author of the " Canones Medicines," a work which 
was translated into many languages, and was the standard 
medical authority for several centuries. 

Writings. — Many manuscripts bear his name, but there is 


doubt as to their genuineness. He divided minerals (chem- 
ical compounds) into : 1. Infusible minerals; 2. Fusible and 
malleable (metals) ; 3. Sulphurous minerals ; 4. Salts. 

There was little that was original in the canons of Avi- 
cenna, the matter coming mainly from the works of Galen 
and Aristotle, but there was a clear and orderly arrangement, 
which gave the chief value to the work. 

Other Arabic Chemists — Avenzoar (eleventh century), a 
Spanish physician, is quoted as making some additions to 
the knowledge of medicinal preparations. In the beginning 
of the twelfth century Averrhoes attained prominence as a 
physician and chemist. The Arabian alchemists of the 
eleventh, twelfth, and thirteenth centuries, who devoted 
themselves to attempts at gold-making, were numerous, but 
of little prominence. Their works are, in the main, unintel- 
ligible, and where the meaning can be puzzled out, contain 
nothing new 


Characteristics of the Age From the thirteenth to the fif- 
teenth centuries may best be called the period of the Arab- 
ists. The decadence of the Moorish power in Europe was 
very rapid. The greater caliphates were broken up into 
smaller dynasties. The Arabs, after a severe struggle, were 
driven from Spain, and Bagdad was conquered by the Mon- 
gols. There was a decline, and then almost complete ces- 
sation from literary work. Still, for some centuries the 
influence of Arabic thought was very great. Their writings 
were translated into Latin and other languages, and formed 
the chief treasures of medical and scientific men. Their 
modes of thought and work were often imitated by their 
monkish successors. The centre of learning began to shift 


westward and northward. Schools and universities were 
established at Montpelier, Paris, Salamanca, Naples, Padua, 
and Toulouse. 

During the previous centuries of intellectual sterility, the 
monks had been the ouly conservators of books and scientific 
works, a dead treasure in their hands. These orders began 
to awaken to intellectual life. The Benedictine order espe- 
cially labored for the spread of knowledge. A medical school 
was founded at Salermo in 1100. During this period also the 
monks preached and led crusades; and, though these did little 
directly for the increase of knowledge, indirectly they greatly 
aided in the spread of Eastern learning and art. 

Many industries were founded by the returned crusaders. 
Alchemy, or the gold-making craze, especially infected them, 
as the nobles were impoverished by wars and the crusades, 
and the urgent necessity was laid upon them of in some way 
replenishing their treasuries. Though the religious orders 
began to show signs of seeking the spread of knowledge, they 
were determined to retain control of the onward march, and 
to allow the progress to go only so far as they saw fit. The 
characteristics of the age were a shameful mental imprison- 
ment and caging of the human reason. Free striving for 
higher light, or criticism of accepted authorities, was looked 
upon as high treason to the Holy Church, and punished by 
the Inquisition. Those who dared to think clearly for them- 
selves, wrote mysteriously for their fellows as a measure of 
safety. Several well-known names fall in this period, amid 
a great number of lesser lights, distinguished by their chosen 
names as monks and the name of the country to which they 
were accredited. Such a one is Richard of England, who 
is mainly noted for having prepared a medicine from gold 
which was warranted to rejuvenate the old, strengthen the 
weak, drive out all sickness, and fend off poison from the 


Albertus Magnus (i 193-1280) Albertus Magnus, or Albert 

of Bollstadt, was the first eminent German chemist. He was 
a Dominican friar and became Bishop of Regensburg. He 
studied at Padua, Cologne, and at Paris, and mastered all 
of the sciences of his day. He was a theologian, physician, 
astronomer, alchemist, and dipped into magic and necro- 
mancy. He was an eloquent and successful teacher. Many 
wonderful feats of magic were recorded of him. He and 
his pupil, Thomas Aquinas, are said to have constructed a 
brazen statue which he animated with his elixir vitce. It 
was capable of walking, talking, etc., like a living being, and 
was very useful as a servant. It was unfortunately very talk- 
ative and noisy. It one day so enraged Thomas Aquinas, by 
constantly interrupting him while he was deeply engaged with 
mathematical problems, that he took a hammer and broke it 
in pieces. Of course this is a fanciful account of a noisily 
creaking automaton, made by these two, who were very fond of 
mechanics, and then, in a fit of dissatisfaction, destroyed by 
one of them. Albertus Magnus lectured in Cologne, and great 
numbers of students flocked to hear him. He skilfully man- 
aged to escape the persecution which befell so many of his 
brother monks who dabbled in the occult art, and was high in 
the odor of sanctity. 

Writings. — His principal writings were the following : 
" De Rebus Metalllcis et Mineralibus ; " " De Alchymia ; " 
" Secretorum Tractatus ;" "Breve Compendium de Ortu 
Metallorum ; " " Concordantia ; " " Philosophorum de Lapide." 

Work and Theories. — He was the first to use the term 
"affinitas " to designate the cause of the combination of the 
metals with sulphur and other elements. The term "vitriol" 
was also first used by him. He regarded the transmutation 
of the metals as an assured possibility. He did not regard 
the metals as distinctly differing substances, but varieties of 
the same species. 


" The metals are all essentially identical ; they differ only 
in form. Now, the form brings out accidental causes, which 
the experimenter must try to discover and remove, as far as 
possible. Accidental causes impede the regular union of sul- 
phur and mercury; for every metal is a combination of 
sulphur and mercury. A diseased womb may give birth to a 
weakly, leprous child, although the seed was good ; the same 
is true of the metals which are generated in the bowels of the 
earth, which is a womb for them ; any cause whatever, or 
local trouble, may produce an imperfect metal. When pure 
sulphur comes in contact with pure mercury, after more or 
less time, and by the permanent action of nature, gold is 

His views are in the main those of Geber, though he adds 
water to mercury and sulphur as one of the constituents of 
the metals. He seems to have combined some of the ideas of 
Aristotle with those of the Arabian school. He was a dili- 
gent and successful worker, and added many chemical facts to 
those known by Geber, as, for instance, the purification of gold, 
the preparation of arsenic, etc. 

Thomas Aquinas (1225-1274) Thomas Aquinas was also a 

Dominican friar. He was a favorite pupil of Albertus Mag- 
nus, and was known as the Angelic Doctor, occupying a high 
place in the church. He was devoted to mathematics and at 
the same time was a great alchemist. He taught at Bologna, 
Rome, and Naples, and wrote several books on alchemy, all of 
which are obscure and unintelligible. His chief treatise was 
the " Most Secret Treasure of Alchemy." He wrote on the mak- 
ing of artificial gems, and, according to some, was the first to 
make use of the term amalgam for alloys containing mercury. 

Roger Bacon (1214-1294). —Roger Bacon was one of the 
most remarkable men of this period. He was born in Somer- 


set, England, and belonged to the Franciscan order. His vast 
store of knowledge won for him the title " Doctor Mirabilis." 
He was a linguist, astronomer, theologian, and mathemati- 
cian. He first drew attention to the error in the Julian Cal- 
endar. He was a skilled optician and mechanic, and made 
several automata. His success in this line brought with it 
the reputation of being in league with the devil, and he was 
severely persecuted while at Oxford. He did not in this have 
the good fortune of Albertus Magnus, or lacked his skill and 
tact. He replied to his accusers by a strong tract, " De 
Nullitate Mar/ice," in which he showed that no such thing as 
magic could exist, and that what his accusers thought were 
the work of spirits were but ordinary operations of nature. 
Still, in spite of his arguments, he was imprisoned ten 

Writings and Work. — His chief writings were : — 

1. " Oj)us Majus." In this his high appreciation is shown 
of the experimental method and the inductive philosophy, 
afterwards advocated by his namesake, Francis Bacon. 

2. " Speculum Alchymice." 

3. "Breve Breviarium de Dono Dei." 

Yet other transcripts are in the British Museum. He 
collected the facts known to the alchemists before his time, 
and followed Geber closely in many things. He knew of gun- 
powder, but speaks of it obscurely. According to some he 
mentions saltpetre and sulphur by name as two constituents, 
and the third constituent under the anagram luru mone cap 
ubre, which is convertible into carbonum pulvere. He prob- 
ably got this knowledge from some Arabic source. He wrote 
thus obscurely and in riddles because of the example of 
others, he said, and because of the dangers of plain speaking. 
No one could appreciate these dangers better than himself. 
Gunpowder was first used by the English at the battle of 
Crecy, more than fifty years after the death of Bacon.. 


His Discoveries. — Roger Bacon was far in advance of his 
age in all branches of science. He is reputed to be the in- 
ventor of the telescope, camera obscura, and burning lenses. 
He subjected organic substances to dry distillation, and 
noticed that inflammable gases were produced; and he 
showed that air was necessary for the burning of a lamp. 
He was an ardent supporter of the belief in the transmuta- 
tion of the metals, and related some very wonderful things 
as to the power of the philosopher's stone. His beliefs 
on these points he drew direct from Albertus Magnus 
and the Arabians. 

Views as to Transmutation. — The following quotation 
from his treatise " Speculum Secretorum " will serve to give 
his ideas as to the transmutation of the metals : " To wish 
to transform one kind into the other, as to make silver out of 
lead, or gold out of copper, is as absurd as to pretend to 
create anything out of nothing. The true alchemists never 
held such a pretence. What is the real problem ? The prob- 
lem is, first, by means of art, to remove from a rough, earthy 
mineral a bright metallic substance, like lead, tin, or copper. 
But that is only the first step towards perfection; and the 
chemist's work must not stop there, for, besides that, he must 
look for some means of getting the other metals, which are al- 
ways present in the bowels of the earth in an adulterated 
condition. For example, the most perfect is gold, which one 
always finds in the native state. Gold is perfect, because in 
it nature finished her work. It is necessary, then, to imitate 
nature ; but here a grave difficulty presents itself. Nature 
does not count the cycles which she takes for her work, to 
which the term of life of a man is but as an hour. It is, then, 
important to find some means which will permit one to do in 
a little time that which nature does in a very much longer 
time. It is this means which the alchemists call, indiffer- 
ently, the elixir, the philosopher's stone, etc." 


Arnold Villanovanus (1235-1312). — Arnold Bachuone, or 
Villanovanus, born either in Provence or Catalonia, was a 
student and later a professor in the University of Barcelona. 
He was an astrologer, among other things; and proving too 
good a prophet in his prediction of the death of the King of 
Spain, he was driven as an exile from that country. He pre- 
dicted the end of the world for 1335, and came under the 
persecution of the church, flying to Paris. From Paris he 
was driven as a gold-maker in league with the devil ; and find- 
ing no resting-place in Italy, he finally sought refuge and 
protection in Sicily. He was shipwrecked and drowned in 
1312, while on a voyage to Borne to heal the Pope, who lay 
sick there. 

Work and Writings. — He was an adherent of the Arabian 
school, believing in the composite nature of the metals and 
their transmutation. He was also a believer in the wonderful 
curative powers of the gold medicine. Under this name went 
many yellow liquids which contained no gold. The aqua auri 
of Villanovanus seems to have been alcohol sweetened with 
sugar and colored yellow with herbs. Yet another of these 
golden drinks was wine in which a glowing plate of gold had 
been cooled. Arnold's chief service was in connection with 
the medicinal use of chemical preparations. He made external 
application of various mercurial compounds, distilled certain 
essential oils, and understood some of the properties of 
alcohol. His knowledge of poisons was extensive. He was 
the first to point out the poisonous nature of decaying flesh. 
His writings are numerous. The principal treatises are 
" Bosarius Philosophorum," " De Vinis" " Be Venenis," 
" Antidotarium." 

Raymond Lulli (1235-1315). — Baymond Lulli was born on 
the Island of Majorca, and was said to be the pupil of Arnold 
and Bacon. He was one of the most eccentric men of his 


times. He belonged to the order of the Minorites, and was 
a most voluminous writer upon alchemical subjects. 

Character of his Work. — Some of his experiments and 
observed facts he describes clearly ; but for the most part his 
writings are obscure and involved, yet with a fantastic and 
picturesque style which led many afterwards to think that 
wonderful facts lay concealed in his treatises. They were 
studied and commented upon, and had great influence. Their 
tendency was toward a sort of combination of religious cant 
with the pursuit of alchemy. For instance, he maintained 
that he only could succeed in preparing the philosopher's 
stone who approached the work with faith and purity. This 
pious or canting tone was greatly affected by alchemists for a 
long time afterwards. The followers of Lulli were called 
the Lullists, and many of their writings were attributed to 
Raymond. He was credited with some four thousand books 
in all, about twenty of which seem to be genuine. He was 
conversant with Geber's works, and often refers to him as the 
Pagan Philosopher. His works are quite unimportant, and 
contained little that was new. 

Growth in this Period. — As to the growth of chemical 
knowledge during this period, we do not find many important 
additions made. Ammonia was discovered, and also alcohol, 
or spirit of wine as it was called. Gunpowder first came to 
the knowledge of the Western nations. Metallurgy and the 
industrial arts, such as pottery, glazing, and glass-making, be- 
gan to improve, and factories to multiply. Apothecaries also 
began as a class to be distinguished from physicians. The 
general tendency of the age was toward magic, sorcery, and 
gold-making. With the exception of a few prominent men, 
there was little attempt at the pursuit of chemistry in a scien- 
tific spirit or for a truly useful end. 



In this period the art of printing was invented, and book- 
making as well as book-owning became easier. In the realm 
of science light became clearer, the desire for knowledge and 
for conquest over nature became greater. Columbus made his 
famous voyage over the unknown ocean, and a new world was 
discovered. Constantinople was taken by the Turks, and 
the learned men gathered there were driven westward with 
their manuscripts and stores of learning. The learning of 
the ancients became a mine of treasure to be zealously 
worked over by monkish students. Scholarly men arose, 
and great discussions were held. The Greek philosophers, 
especially Aristotle, ruled the thought of the day. Still there 
was much to hamper progress. The work of these scholiasts 
was almost exclusively commenting upon and elucidating the 
earlier writers, with as little idea of adding to their writings 
or their knowledge as to the Holy Scriptures. What was 
called the " Unholy Quest of Alchemy " had greatly increased 
in extent. It pervaded all ranks, and caused great misery, 
deceit, and loss. In the Roman provinces, in England, and 
elsewhere, it was most rigidly forbidden by law ; but these laws 
were evaded. 

Several English names occur in this period, as George 
Ridley, Canon of Bridlington, who wrote a poem on alchemy, 
and was reputed to have been successful in the search for the 
wonder-working stone. Thomas Norton was another English 
writer on alchemy. 

Basil Valentine (1394-) Above all others stands the 

name of Basil Valentine. So much doubt has been thrown 
around the personality of this alchemist, that some have even 
denied his existence. He seems to have lived in Erfurt, how- 


ever, and to have been a monk of the Benedictine order. In 
his writings he shows some similarity to Lully. He had 
largely the same ideas as to the healing power of the philoso- 
pher's stone and the peculiar spirit in which the search for 
the same should be made. He maintained that its discovery 
was to be a reward of piety. There was an identification of 
the spiritual with the material, of life with chemical processes. 
He was a strange mixture of a cool observer and a maudlin 
dreamer. In general, however, he had a clearer view and 
made a plainer path in alchemy and in medicine than his 

Work and Theories. — He showed especial skill in connect- 
ing experiments, following up some distinct line of thought. 
He made much progress in observing the action of medicines, 
and this at a time when there was very great abuse of medi- 
cines and poisons by physicians. He added salt to Geber's 
list of constituents of the metals. His knowledge of the 
metals was great. For the first time arsenic, bismuth, and 
zinc are distinctly mentioned and classed with the metals, 
though arsenic was discovered earlier. But his greatest dis- 
coveries were in connection with antimony and its compounds. 
In his book, entitled the " Triumphal Car of Antimony," these 
discoveries are described. Antimony was prepared by the 
ancients ; but it was confused with the other metals, and was 
practically unknown to them. Basil Valentine first tells of 
its preparation and makes use of the name. The metal was 
used in purifying gold, and the compounds were applied me- 
dicinally. Through his use of these he wrought many cures 
and acquired great reputation. Hydrochloric acid was first 
prepared by him by heating together copperas and salt. He 
made use of precipitation as a method of experimenting, 
either discovering it or first largely applying it. Also the 
first attempts at qualitative analysis are due to him. He 
proved that iron was present in certain hard tins, copper in 


Hungarian iron, silver in Mansfield copper, and gold in Hun- 
garian silver. The spirit lamp was used by him in his work, a 
great step forward and a marked improvement upon the 
cumbrous furnace. 

Writings. — His chief writings are : " Currvs triumphalis 
Antimonii ; " " De magno Lapide Antiquorum Sapientum ; " 
" Apocalypsis chemica ; " " Testamentum ultimum ; " and 
" Conclusiones." 

An example of his method of experimentation may be 
gotten from his "Marriage of Mars and Venus." This oper- 
ation consisted in dissolving filings of iron and copper in oil 
of vitriol, mixing the two solutions, and allowing them to crys- 
tallize. The vitriol produced contained both iron and copper. 
This vitriol subjected to calcination gave a scarlet powder 
(mixture of red oxide of iron and oxide of copper). It was 
this powder which should furnish the mercury and sulphur of 
the alchemists. " Take this powder in a distilling vessel well 
luted and heat gradually. There is first obtained a colorless 
spirit which is the Mercurius Philosophorum, then a red spirit 
which is the Sulphur Philosophorum." Again in another 
place he says, "Antimony is the bastard of lead ; bismuth or 
marcasite is the bastard of tin." 


The alchemists characterize this age. We find among 
them the genuine enthusiast, who labored unceasingly with the 
firm belief in the ultimate success of his search, if only he 
could hit upon the right way. There was something of the 
fascination of a lottery in it, along with the nobler feeling of 
earning success by work. Any one experiment might result in 
the wished for discovery, and bring with it untold wealth and 
freedom from pain, and even, it might be, a victory over death 
itself. The devotees to the search were led on and on, until 
fortune and life sometimes were sacrificed in the quest. 


Growth of the Belief in Transmutation The belief in the 

transmutation of the metals was a natural outcome from the 
Greek theories as to the elementary principles. The Greek 
doctrines, as represented by Aristotle, were taught in all the 
great academies, and could easily be construed into meaning 
that gold and silver could be produced from the baser metals. 
It seems strange that truly learned men, as Geber, Villanova- 
nus, Bacon, and Valentine should have believed in the exis- 
tence of a philosopher's stone, a substance so powerful that a 
bit of its dust thrown upon melted base metals could trans- 
mute them into gold and silver. 

Confirmation of the Belief We must remember, however, 

that there were many remarkable phenomena known to them 
for which this theory offered the simplest explanation ; every- 
day phenomena they are to us, and their explanation seems 
very simple in the light of our wider knowledge. 

Thus, we have certain changes of color in metals produced 
by the addition of other bodies. Geber knew that when red 
copper was melted with tutty (an impure oxide of zinc) golden 
yellow brass was produced, and certain other minerals (which 
we now know contained arsenic) gave this same metal, cop- 
per, a silvery white color. Of course it was known that these 
were not gold and silver, but the possibility of some sort of 
transmutation seemed proven. Again, iron dipped into water 
containing bluestone was changed into copper. Geber be- 
lieved that when mercury was added to lead, tin was pro- 
duced, the solid amalgam having very much the appearance 
of that metal. 

The metallurgical operations of those days were very im- 
perfect, and not at all understood ; so that the fact that a 
bead of silver was gotten from certain galenas, and gold from 
copper ores and from pyrite, was looked upon as a proof of 
the changes of the base metals into the noble by some of the 


operations during the treatment. It was not until many- 
analyses had been made in later years that this was given 
up as a proof of transmutation. These experimental proofs 
were further supported by much historic evidence. 

Traditions as to Gold-making Traditions and stories of 

wonderful character and most circumstantially related, all 
combined to confirm this belief. One such story may be 
given as copied by Thomson from Mangetus. 

" A stranger, meanly dressed, went to Mr. Boyle, and, 
after conversing for some time about chemical processes, re- 
quested him to furnish him with antimony, and some other 
common metallic substances, which then fortunately happened 
to be in Mr. Boyle's laboratory. These were put into a cru- 
cible, which was then placed in a melting-furnace. As soon 
as these metals were fused, the stranger showed a powder to 
the attendants, which he projected into the crucible, and 
instantly went out, directing the servants to allow the crucible 
to remain in the furnace till the fire went out of its own 
accord, and promising at the same time to return in a few 
hours. But as he never fulfilled his promise, Boyle ordered 
the cover to be taken off the crucible, and found that it con- 
tained a yellow-colored metal, possessing all the properties of 
pure gold, and only a little lighter than the weight of the 
materials originally put into the crucible." 

Theories as to the Origin of the Metals There were many 

attempts at explaining the origin of the metals. Thus we 
have Geber's sulphur and mercury theory, elaborated and 
added to by later alchemists. It is noteworthy that these 
constituents were volatile. Basil Valentine speaks of them as 
" condensations of a mere vapor into a certain water." Some 
said that the sun acting upon and within the earth formed 
the metals, and that gold was merely its beams condensed 


to a solid. The belief that metals grew as vegetables 
was very common, and dated back to prehistoric times. It 
was customary in the Middle Ages to close a mine from 
time to time, and thus give the metals opportunity for 

Legal Prosecution of the Gold-makers Sometimes the aid 

of the law was invoked to suppress the pursuit of alchemy, 
in many cases because the government feared the possession 
of any such potent secret on the part of a subject ; in others 
because it was impious or contrary to the interests of the 
church. In 1404, by an Act of Parliament, it was forbidden 
vto make gold or silver. Patents were granted later by Henry 
IV. to certain persons who claimed to have discovered the 
philosopher's stone, and a commission of ten learned men 
was afterwards appointed to determine if this transmutation 
of base metals into gold were possible or not. 

Mystical Language Legal prosecution, and the desire to 

keep their wisdom in a form intelligible only to adepts, as 
well as a desire to appear to be wise where no wisdom really 
was led to the adoption of a secret mystical language, vari- 
ously interpreted from one generation to another, and unin- 
telligible to chemists of the present day. The obscurity was 
much increased by the multiplication of symbols. These 
were often drawn from astrology and other sciences. Rod- 
well records one Italian MS. of the early part of the seven- 
teenth century, in which mercury is represented by twenty-two 
distinct symbols and thirty-three names, many of which are 
of distinctly Arabic origin, such as Chaibach, Azach, Jhu- 
mech, Caiban, etc. 

Sharpers and Charlatans. — Of course many sharpers and 
charlatans sprang up, pretending to possess great knowledge, 


to hold the wonderful secret of alchemy, and to be able to 
make gold without limit. Pieces of gold said to have been 
made by these adepts are still preserved in several of the 
museums of Europe. In some cases the frauds were discov- 
ered. Crucibles with double bottoms, nails hollowed out and 
filled with powdered gold, mercury or lead containing gold, 
and similar devices, are recorded. The delusion has proved a 
lasting one. Alchemists have deceived themselves and others 
in this century, and even in the last quarter of it some have 
come within the grasp of the law. 

Adepts. — Among the genuine alchemists there was a 
secret and mystical language in use, intended for the initiated 
and adepts only. They had the same mottoes in their work- 
shops. The old Greek idea of the impelling force of the 
universe was exemplified by the avayK-q written on their 
walls. On another side, or over the furnaces, would appear 
the Latin exhortation, Spira, Spera, or Ora, Labora. 

The Universal Medicine The making of gold was their 

first great aim, but not their only one. They sought also the 
universal medicine which should cure all diseases, and the 
elixir vitm, which would fend off the encroachment of old age. 
This belief in a universal medicine is more difficult to trace 
than that in the transmutation of the metals. It may have 
been a mistake arising from the Oriental imagery of the early 
Arabian writers. These did not seem to hold the peculiar 
doctrines of the elixir vitas. They called the base metals 
diseased, and spoke of healing their diseases. Thus Geber 
says, " Bring me six lepers that I_ may heal them ; " that is, 
transmute~the~six base metals into gold] The discovery of 
remedial agents among the salts, or so-called minerals, 
strengthened greatly the belief in the healing powers of the 
philosopher's stone. 


Other Aims Other objects of search were the universal 

solvent, and the lamp that would burn forever. All such fan- 
cies seem to us very childish, but in all ages the wonders of 
science have seemed very marvellous, and have been attrib- 
uted to magic ; and then, too, half-knowledge is generally very 
credulous. The average newspaper of to-day will count 
among the possible achievements of the near future things as 
impossible as the dreams of the old alchemists. And again, 
what dreams or wildest fancies of theirs could have exceeded 
what science really has accomplished with its steam and 
electricity and light. The chemist of the present dreams of 
all metals being but varying forms of the same matter or 
matters, and gropes his way backward to some primal element. 




Paracelsus and his followers formed a sort of transition 
from the alchemists of the Arabic school to the iatrochemists. 
This, the sixteenth century, was characterized by restless 
adventure and discovery. The wilds of America were being 
explored, the sea route to India was discovered. There was 
a breaking loose from the authority of the church and of 
the Grecian philosophers. The Reformation of Luther, the 
discoveries of Copernicus, fall in this age. The great uni- 
versities were beginning to make their influence felt : Oxford 
had been founded in 1300, Heidelberg in 1346 ; and these 
began to be centres of light and learning. There was a ten- 
dency to unite chemistry and medicine. Life processes and 
changes in the body were accounted for on chemical grounds. 
Medicine was, in a measure, a branch of applied chemistry, 
and then it began to be looked upon as the true end of chem- 
istry. The consequence was that researches were more care- 
fully made, and new compounds were discovered. A new 
object and zest were given to the study, and chemistry became 
the pursuit of cultivated men. 

The dominant chemical theory determines the character of 
the work done in any period. Alchemy was a natural deduc- 
tion from Geber's theory of the nature of metals. Now 
elements began to be regarded as distinct bodies, capable of 
preparation and examination ; and the Aristotelian idea of 



their being the unmakable causes of certain peculiar proper- 
ties or characteristics was gradually given up. 

Paracelsus (1493-1541) Philippus Aureolus Theophrastus 

Paracelsus Bombastus von Hohenheim was born at the little 
Swiss town of Marie-Einsiedeln. His father was a physician 
of good family. All Europe was stirring with the revolt 
against hitherto accepted authorities in church and state. 
Luther and Calvin were fighting their great battle against 
error and superstition. Copernicus was remodelling astron- 
omy on a new system. Paracelsus was also a noteworthy 
reformer, and has been called the Luther of medicine. His 
early youth was spent under the tutelage of his father. At 
sixteen he entered the University of Basel as a student; 
and he also studied under the well-known alchemist, Frithe- 
mius, from whom he acquired his bent for occultism. He made 
prolonged journeys through most of the known countries of 
the world, going beyond India. He was taken prisoner by 
the Tartars, and remained with them a number of years. 
Wherever he went, he sought to glean every scrap of knowl- 
edge obtainable from those with whom he came in contact. 
Tn his thirty-fifth year he was chosen professor of medicine in 
the University of Basel. His striking originality and freedom 
of thought brought him many enemies, especially among his 
colleagues. The writings of Galen, Avicenna, Hippokrates, 
and others, so much revered by the great mass of physicians 
and scholars, were gathered by him and publicly burned. This 
and his freedom of thought in religious matters led to a perse- 
cution by his enemies, which drove him from the university, 
and forced him to take up once more a wandering existence. 
He is reported to have met a violent death in the town of 
Salzburg at the hands of assassins employed by his opponents. 

The Character of his Work. — He was constantly active as 
teacher, physician, and author, and is said to have written over 


one hundred books. He has been accused of drunkenness, 
impiety, roughness, and trickery in performing his cures ; but 
much of this can be set down to the malice of his enemies. 
He not only abjured the authority of the ancient philosophers 
and physicians, but also chose German, the language of the 
people among whom he lived, as the vehicle of his thoughts, 
giving up the monkish Latin. His opponents said this was 
because he knew no Latin. His works, printed and in manu- 
script, cover many subjects — medicine, chemistry, botany, 
philosophy, physics, astronomy, astrology, and magic. Many 
of these seem to have been dictated to his pupils, or to have 
been notes taken on his lectures. He was not fond of am- 
biguity of expression, but was for the most part short, con- 
cise, and clear in his style; and his writings are marked by 
energy and enthusiasm. 

As a Physician. — He was most skilful and successful as a 
physician, introducing a new theory and system. All dis- 
eases, according to the prevalent idea, came from excess in 
either bile, phlegm, or blood. Paracelsus maintained that each 
disease had its own definite existence, with definite cause and 
sequences, and must be antagonized by specific remedies. 
This was the inaguration of the modern method of combating 
disease. No progress was possible until this view of its na- 
ture was adopted. He was the first to apply the magnet in 
disease, and anticipated Mesmer in his discovery of animal 
magnetism, or mesmerism. He believed in one universal prin- 
ciple, life, and that all organic functions were caused by it. 
He could not wholly separate himself from the belief of his 
times, so that much that is foolish and incomprehensible is 
mixed with his science. Much of his mystic philosophy he 
brought back from India and the East, and some of his writ- 
ings resemble a good deal the Theosophism of to-day. 

As a Chemist. — Paracelsus was by far the most approved 
chemist of his times. All that was then known of analytical 


methods he had made his own, and he added much to them 
that was important. To him the first discovery of hydrogen 
is accredited, though of course it could not be called a discov- 
ery in the sense of preparing and identifying the gas. The 
foundation for a classification of the metals which lasted for 
many generations was laid by him. He was largely instru- 
mental in turning chemistry from wasteful aims to became an 
adjunct of medicine. 

Contributions to Pharmacy. — Pharmacy as a distinct pro- 
fession and object of study was largely founded by him. It 
is astonishing how many new and valuable remedies were in- 
troduced by him. Mercurial preparations, lead compounds, 
iron salts, arsenic for skin diseases, milk of sulphur, bluestone, 
and many others, might be mentioned. Various vegetable 
medicines had been hitherto used in the form of decoctions or 
simply sweetened with sugar. He began the search after the 
active principles of these plants, and brought them into use as 
tinctures, essences, and extracts. Tincture of opium was first 
prepared by him, and given its present name of laudanum. 

Extracts from his Writings. — Two or three extracts may 
be given from his works. First as to air : " When wood burns, 
air is the cause of it. If there is no air, then the wood will 
not burn." 

He noticed the appearance which is seen when oil of vit- 
riol acts upon a metal, and spoke of the evolution of the gas 
as the " rising of a wind." This is the first notice of hydrogen. 

" Metals," he says, " are composed of three elements, — the 
spirit, the soul, and the body; in other words, mercury, sul- 
phur, and salt. Dead metals may be revivified or reduced to 
the state of metals by means of soot." 

His Followers. — The Paracelsists, who arose afterwards, 
seem to have been largely mystics, and have been confused 
with the Rosicrucians. The name was also applied to such 
physicians as defended his medical views. They often copied 


the roughness and the wandering life of their master, but 
were without his mental gifts. Some were alchemists and 

Thurneyser was one of the more noted of the Paracelsists. 
He was a physician of Berlin, and defended the views of Para- 
celsus, but his contributions to chemistry were unimportant. 

The views of Paracelsus met with especial opposition from 
the Paris medical faculty, though Quercetanus and Turquet 
de Mayerne stood up for their defence. These and others had 
little critical ability, so that there was no attempt at separat- 
ing the false from the true in the philosophy of Paracelsus. 

Libavius (1540-1616) The first to put these matters to 

the proof was Andreas Libau, or Libavius. He was born at 
Halle, and there studied medicine and settled as a physician. 
He did not stay there long, changing both residence and pur- 
suits, though still keeping up his medicine and chemistry. 
Libavius is distinguished from most of the Paracelsists by his 
temperate language and independent spirit. He fully believed 
in the transmutation of the metals. Still, he did much to 
point out the meaningless nature of the mystical writings of 
the Paracelsists, and the worthlessness of many of their reme- 
dies and medicinal preparations. He made many valuable 
chemical discoveries. Sulphuric acid was first prepared by 
him by burning sulphur and saltpetre, and he showed that 
this was contained in the various vitriols and was the same 
as oil of vitriol. He discovered the tetra-chloride of tin, which 
is still called Spiritus fumans Libavii. He wrote the first text- 
book of chemistry, which put, clearly and in order, all that be- 
longed to the science. This was frequently reprinted, and 
held in high esteem for a long time. 

Agricola (1494-1555) Contemporaneous with Paracelsus, 

but forming a strong contrast to him, was the distinguished 


technical chemist George Agricola, who was born near Meis- 
sen. He studied at Leipsic, and attended the Italian universi- 
ties. He was a physician, but devoted his attention more 
particularly to the advancement of metallurgy and the indus- 
trial arts. Many improvements were introduced by him. He 
wrote little on medical subjects, and took no part in the hot 
strife over the revolution of Paracelsus. 

His works are characterized by clearness and intelligi- 
bility. His chief work is called, " De Re Metallica," and is 
a connected treatise on metallurgy. This went through many 
editions, and was for a long time considered an authority on 
the subject. Agricola had no contemporary pursuing a like 
course of study and work. He was the first and for a long 
time the only industrial chemist ; and his book is very useful 
as giving a clear account of the conditions of the various in- 
dustries in his day, and the different methods and operations 
in use then. 


Paracelsus and his followers had turned chemistry into 
new lines. In the years following this new aim was con- 
firmed, and chemistry became an adjunct to medicine. The 
position held by it was subordinate to that of the healing art. 
The chief object of research was the finding of new medi- 
cines, or the explanations of natural processes. Hence the 
name given to this period is that of the iatro-chemists or 

Van Helmont (1577-1644). — The first of these and the 
most distinguished was John Baptist Van Helmont, who 
was born in Brussels, and belonged to one of the aristo- 
cratic families of Brabant. He studied at Louvain, and 
showed both brilliancy and eccentricity of intellect. He was 
much attracted by the mysticism of the earlier writers, and 


was led to renounce rank and property, and practised medi- 
cine as a work of charity and benevolence. He became dis- 
gusted with the system of the Galenists, and resolved to 
reform medicine as Paracelsus had done. His knowledge be- 
ing greater, he was not satisfied with the works of Paracelsus. 
After travelling through France and Italy, and returning 
home, he married a rich lady, and spent the remainder of his 
life at work in his laboratory. 

His Theories. — Van Helmont considered water as the 
primal principle or element, and brought forward many in- 
genious arguments in support of his theory from the animal 
and vegetable world. He performed the famous experiment 
with the willow, and it is the most plausible among his ex- 
periments adduced as proofs of his theory. He took a large 
earthen vessel, and filled it with two hundred pounds of dried 
earth. In it he planted a willow weighing five pounds, which 
he duly watered with rain and distilled water. After five 
years he pulled up the willow, and found that it now weighed 
one hundred and sixty-nine pounds and three ounces. The 
earth had decreased two ounces in weight. Thus, according 
to his reasoning, one hundred and sixty-four pounds of root, 
bark, leaves, etc., were produced from water alone. Fish, he 
said, live on water, and yet they contain all the peculiar 
animal substances. These are then made from water. 

Study of the Gases. — He introduced the term gas to dis- 
tinguish water vapor and other elastic fluids from the air, and 
was the first to study aeriform bodies. The vapor coming 
from fermentation, that is, carbon dioxide, he called gas 
sylvestre. He recognized other gases, gas pingue, etc., and 
was the first one to attempt any study of these most interest- 
ing bodies, dividing them into inflammable and non-inflam- 
mable. As he was ignorant of any method of collecting 
and separating them, his knowledge was very imperfect. 
He even maintained that gases could not be imprisoned in 


any vessel, but would penetrate anything in order to mix 
with the surrounding air. 

Views on Transmutation. — He denied the truth of the 
theory, so long prevailing, that the metals were composed 
of salt, sulphur, and mercury. He rejected and overthrew 
the Aristotelian four-element theory, proving that fire was 
no element, and that cold and warmth were not material. 
Further, he found that a substance could enter into many 
different combinations without losing its peculiar properties. 

Ideas of Physiology. — His ideas of physiology were, of 
course, very crude, but still an advance upon those of Para- 
celsus. He believed in curing diseases by dietetics, by 
working on the imagination, by incantations, etc. ; still, he 
made use of chemical preparations, and greatly advanced 
them in popular favor. He believed in the transmutation of 
metals and in magic Much of this came from the mysticism 
in his early training. He was even more of an enthusiast 
than Paracelsus, accounting himself appointed of God for the 
reform of medicine. He believed that he had once seen his 
soul as a brightly shining crystal. Mice, he thought, could 
be made by placing a soiled shirt with some flour in a barrel 
or other vessel. He claimed to have the philosopher's stone 
and the alcahest, or universal medicine, in his possession, but 
declined to write out clearly their modes of preparation. His 
works were collected and published, after his death, by his son, 
under the title, " Ortus Medicinal vel Opera et Opuscula Om- 
nia." This was translated into French, English, and German. 

Sennert (1572-1637) In Germany and the Netherlands 

the greater part of the distinguished physicians came over to 
the views of Van Helmont. Among them was Daniel Sennert, 
professor of medicine at Wittenberg. He did much to recon- 
cile the adherents of the Hippokratic school to the new 
medicine, pointing out that it did not do away with the facts 


learned empirically under the old system, but attempted to 
clear up and explain them. 

Glauber (1604-1668) A more distinguished name is that 

of Johann Rudolph Glauber. Very little is known of his 
life and surroundings, beyond that he lived in various German 
towns and then went to Holland, dying in Amsterdam. His 
early education was much neglected, and his writings show 
him to have been a strange mixture of a sharp observer and a 
mystery-loving braggart. He believed fully in the aims of 
alchemy, but does not seem to have pursued them himself. 
He discovered and introduced many chemical preparations, 
preparing, for instance, purer and stronger hydrochloric and 
nitric acids than had been prepared before, and at the same 
time discovering sodium sulphate, to which he ascribed won- 
derful curative powers, and gave it the name sal mirabile. It 
is still called Glauber's salt. Various other sulphates and 
chlorides were first prepared by him. 

Theory of Double Decomposition. — His observations upon 
double decomposition are interesting. " Aqua regia which 
has taken gold into solution kills the salt of tartar (potash) of 
the liquor of flints (silicate of potash) in such a way as to 
cause it to abandon the silica, and in exchange the salt of 
tartar paralyzes the action of the aqua regia in such a way as 
to make it let go the gold which it had dissolved. It is thus 
that the silica and gold are both deprived of their solvents. 
The precipitate is composed, then, at the same time of gold 
and of silica, the weights of which together represent that of 
the gold and of the silica originally employed." 

Suggestions for Industrial Improvements. — He also showed 
interest in technical methods, and made many improvements 
in them. He first recommended the use of what are called 
Hessian crucibles. He was an ardent patriot, especially 
desirous that Germany should learn to manufacture her own 


crude materials. His improvements in glass-making and in 
the use of mordants deserve especial mention. He wrote 
several books in the German and Latin languages. 

Sylvius (1614-1672) Sylvius (Franz de la Boe) was an- 
other influential man of this time. He was born at Hanau, 
though he was of a Dutch family, and his life was mainly 
' spent in Holland. In learning and culture he was above all 
of his predecessors, and he ably filled a professorship in the 
University of Leyden. His views were in the main those of 
Van Helmont, with the mysticism and spiritualism left out. 
His life was mainly devoted to medicine, but still he was a 
skilled chemist. He accepted the belief of his times in gold- 
making and in the alcahest. Other names of this period are 
Tachenius, Thomas Willis, etc. ; but it is unnecessary to speak 
of these in detail. 

Mistakes of the Iatro-chemists Two mistakes were made 

by the iatro-chemists. They attempted to explain, on chem- 
ical principles, all the changes and processes going on in the 
body. This was certainly not possible for the chemistry of 
that day. To Van Helmont, for instance, disease consisted in 
the excess or preponderance of base or acid in the juices of 
the body. Secondly, too narrow a limit was set to chemistry. 
It was destined to fill a much larger sphere than to be an 
adjunct to any other science. 


The science could not long remain in this subordinate 
position. It so grew in extent and importance that it was 
able to burst the bonds of its too close alliance with medi- 
cine, and take for its field the study of the combinations 
and decompositions of all known substances. The induc- 
tive philosophy of Francis Bacon began to have its due 


effect. Chemistry assumed its proper place as a science. 
Its study was no longer obscured by gold-hunting, nor limited 
to the concoction of medicines. It was an age of qualitative 
chemistry, a step towards the higher quantitative work of the 
next era, and an immense step forward from the haphazard 
chemistry of the past. There are, of course, many dangers in 
relying on qualitative tests alone, and many mistakes were 
made during this period. The guiding principle of the work 
seems to have been the dictum, similar appearances are due 
to similar causes, a saying which carries with it much of 
plausibility, and yet might lead into serious error. 

Phlogiston Theory The theory as to combustion phenom- 
ena, rightly regarded as the central processes of chemistry, 
called the phlogiston theory, especially characterized this 
period. This theory was gradually evolved, was imperfectly 
stated by Becher, elaborated by Stahl, and attained complete 
domination only toward the latter part of the eighteenth cen- 
tury. The existence of a combustible principle, named phlo- 
giston, was assumed in all combustible bodies. The residue 
left after combustion was supposed to be a constituent of the 
original substance. Thus the acid substance gotten on burn- 
ing sulphur was supposed to have existed in the original 
sulphur, and sulphur itself was a compound of this with 
phlogiston which escaped in the burning. The calcination of 
the metals was regarded as a process analogous to combustion, 
and hence to be explained in the same way. The resulting 
body, which we call an oxide, was called a calx. The 
original metal, then, was, in the eyes of these chemists, a 
compound of this calx with phlogiston. The more energetic 
the combustion, the more phlogiston did the body contain. 
Coal, for instance, was regarded as containing a great deal. 
Phlogiston could be restored by bringing together a calx and 
a body rich in phlogiston. Thus a metallic calx heated with 


coal yielded the original metal. This theorizing as to phlo 
giston resembles in its methods the dreaming of the Greek 
philosophers, who preferred to base their theories on pure 
reasoning rather than on observation and experiment. No 
attempt at first was made at the isolation of phlogiston, nor 
were experiments adduced in support of the theory. Efforts 
of this kind were only brought out by the vigorous attacks of 
opponents in the last stages of the controversy over the theory. 
There were various suppositions as to the nature of this phlo- 
giston, some of them ridiculous. Thus it was identified with 
light or flame, with the coloring matter of Berlin blue, and 
with hydrogen. This last identification was the latest made, 
and was more the result of experiment, and hence was the 
more difficult to disprove. For instance, a metal was observed 
to give off hydrogen when acted upon by an acid. Now, 
hydrogen acted upon hot calces and restored the original 
metal. Lastly, a calx united with an acid to give a salt. The 
supposition that the metal was a compound of hydrogen and 
the calx is then very plausible. 

General Characteristics of the Period. — There was not an 
entire breaking away from the sister science which had done 
so much to lift chemistry from the mire of alchemy. It was 
still useful to medicine and pursued by physicians, only its 
horizon was wider by far than ever before. Nor was alchemy 
dead. Many were still infected by the craze of the old al- 
chemists, but the work was largely secret and looked down 
upon. The line was a distinct one between alchemy and 
chemistry, and their courses diverged more and more widely. 
Many learned societies were founded in this age, usually cen- 
tring at the seat of some great university. By the bringing 
together of men of like pursuits, and the publication of their 
memoirs, they proved powerful incentives to the advancement 
of science. The most notable of these has been the Boyal 


Society of England, founded in 1645 by Charles II. Among 
others were the French Academy, the Swedish Academy, and 
the Royal Society of Berlin. All of the great scientific men 
of this time were connected with one or the other of these, 
and gave to the world their discoveries through their peri- 
odical publications. 

Boyle (1626-1691) First among the names of this age 

stands that of Robert Boyle. He was born in Ireland in the 
year 1626. His father, the Earl of Cork, intended him for 
the ministry, and his studies took that direction. He received 
his education at Eton and at home. Afterwards he travelled 
for six years on the Continent, spending two of them in 
Geneva. The political and other troubles in his native land 
called him home, and he returned to find his father dead. 
The fortune left him sufficing for his modest needs, he retired 
to his estate in England, and devoted his time to work upon 
his favorite studies, physics and chemistry. He went to 
Oxford, where he aided in the foundation of the Royal 
Society. His life was spent quietly and uneventfully, part 
of the time in Oxford, and part in London, and was devoted 
to scientific work of high order, to fostering the aims of the 
society, of which at one time he was offered the presidency 
but declined, and to works of benevolence and charity. Boyle 
was the first to pursue the study of chemistry from the noble 
desire for a deeper insight into nature. Not the craze for 
gold, nor the wish to apply his knowledge to any art or 
industry, but the earnest desire for truth, inspired him. 

Character of his Work. — He antagonized the alchemists, 
except in respect to a belief in the transmutation of the 
metals, and also contended with the iatro-chemists, refuting 
some of their doctrines, though he agreed with Van Helmont 
that one must look to chemistry for the solution of the 
greatest problems of medicine. He was the first to apply 


Bacon's inductive method in its fulness to the science. He 
maintained that experiment alone was the proper basis for 
theory, and that all theories must be tested by experiment. 
Before attempting any theorizing himself, he set to work to 
correct the faulty experiments and imperfect observations of 
others, and so to clear the road for true knowledge. 

Experiments upon Air. — His experiments were largely 
upon air and water, choosing two of the commonest and yet 
most instructive substances in nature. The knowledge of the 
first, physically and chemically, was greatly advanced by him. 
He made use of and improved the air-pump, and examined 
the behavior of different bodies in vacuo. He enunciated the 
famous Law of Pressure upon Gases, still known as Boyle's 
Law. He experimented upon the height and weight and 
density of the atmosphere. Furthermore, he showed that 
something in the air was destroyed by breathing, or by the 
burning of a body in it. This was, of course, only a veri- 
fication of an observation made long before. He proved that 
an increase of weight was caused by calcination, and that the 
calx was specifically lighter. The calcining of such a body 
as lead, he showed, consumed air. It is strange how near his 
experiments brought him to important truths. He was not 
happy in the interpretation of his results, however. He could 
see many faults in the theories of the times, but seldom felt 
his way clear to establishing a theory of his own. 

Constitution of Matter. — His ideas as to matter were much 
like the present. He considered all bodies to consist of very 
small particles, and that the union of these particles gave 
compounds. Decomposition was impossible until the attrac- 
tion between them had been overcome. According to this 
hypothesis, the differences between bodies was due to the 
inequalities in the form, structure, and movement of the ele- 
mentary molecules. One or two primal elements would suffice 
to explain all the varieties of bodies in nature. Thus, he 


supposed, the molecules of water may, in certain conditions, 
be so grouped and set in motion as to form the body we call 
air. It is easy to see that all through the ages one of the 
great puzzles set for thinking men has been the invisible 
atmosphere surrounding us, forming and buoying up its cloud 
masses, and pouring down its floods of water or hail or snow. 
He knew the relative affinity of various metals towards the 
acids. A chemical compound was defined by him as one formed 
by the union of two or more components which lose their 
properties, the compound having new and different properties. 
Improvements in Qualitative Analysis. — He systematized 
qualitative analysis, arranging bodies into classes or groups. 
Vegetable coloring matters were used by him as indicators for 
acids and bases. Regular reagents were introduced by him 
with directions for their use. Many of his tests we make use 
of at the present day, as, for instance, ammonia is driven out 
by lime or caustic potash, and tested for by its fuming with 
hydrochloric acid. His chief writings were the " Sceptical 
Chymist," " Experiments and Considerations Touching Colors," 
and " Memoirs for the Natural History of Human Blood." 

Kunckel (1630-1702) Johann Kunckel was a contem- 
porary of Robert Boyle, but not his equal in learning. He 
was born in Holstein, where his father was supported by the 
duke as an alchemist. He was largely active in pharmaceu- 
tical and technical chemistry, and was at different times in 
the service of several princes as alchemist and gold-maker. 
In this there seemed to be no intention to deceive on his part, 
but an honest working for his employers, and often with 
them, over what he regarded as a possible problem. Later 
he writes as to the transmutation of the metals : " In chem- 
istry we have separations, combinations, and purifications, but 
never transmutations. The egg is hatched by the warmth of 
the hen. With all our art we cannot make an egg. We can 
destroy it and analyze it, but that is all." 


He was at one time professor of chemistry at the Univer- 
sity of Wittenberg, and died in Sweden, where he had held 
high position in connection with the mines, and had been 
raised to the nobility. 

His Work. — Kunckel did not originate nor add much to 
the theories of the times. He demanded facts, first of all, 
and left theorizing to others. He aided more by his observa- 
tions and experiments in overthrowing the old theories, and 
he made some important additions to chemical knowledge. 
One of his greatest achievements was the discovery of the 
mode of preparing phosphorus, the element having been 
really discovered by Brand, who showed it to him, yet held 
the method of preparation secret. This discovery was made 
by Boyle at the same time. 

Becher (1635-1682) Johann Joachim Becher was a fel- 
low-countryman of Kunckel. His father was a clergyman ; 
he himself was a physician, leading a wandering life and dying 
in England. His work consisted not so much in the discovery 
of new facts, as in the collating of those already known and 
their explanation. His writings are mainly theoretical. He 
believed in alchemy, but maintained that science was dearer 
to him than gold, and wisely refused to make the gold search 
the object of his work. 

His Theories. — His important chemical theories are those 
in connection with the constitution of bodies and combustion. 
All inorganic substances were, in his estimation, of an earthy 
nature. There were three fundamental elements of which 
the metals and minerals were composed : an earth vitreous 
and transparent ; an earth mercurial, subtle, and volatile ; and 
a principle igneous and combustible. These, with water, gave 
rise to a primal acid, which was the generating principle of all 
acids. Becher wrote many works on various subjects. His 
writings and theories were brought to notice afterwards by 


Stahl, and had great influence upon the development of chem- 
istry. It was from Becher principally that Stahl got the 
germ of the phlogiston theory. 

Homberg (1652-1715) Two members of the French Acad- 
emy became prominent at this period, Lemery and Homberg. 
The French Academy of Science had been founded in 1666 
by Colbert, the minister of Louis XIV., but did not publish 
its memoirs until nearly forty years afterwards. Homberg 
was a lawyer, but gave up the practice of his profession to 
study natural science and medicine. He knew both Boyle 
and Kunckel, and was a good observer and skilful in carry- 
ing out his experiments, but a poor interpreter of results. 
He held to the ancient theories, and took little part in 
establishing the new. He contributed a large number of 
papers on chemical, zoological, botanical, and physical sub- 
jects to the French Academy. 

Lemery (1645-1715). — Nicholas Lemery was especially 
renowned as a teacher, though he was also a good worker, 
dealing in the practical rather than the theoretical. His 
son, Ludwig Lemery, was also a distinguished chemist. The 
elder Lemery's greatest work was the writing of his text- 
book of chemistry, " Cours de Chimie" (1675), which em- 
braced all that was known of chemistry, and endeavored to 
give a suitable connection between the facts recorded, and 
to systematize them. This was for many years the best 
text-book on the science, and was issued in repeated editions 
as the science advanced. Thirteen editions appeared during 
the author's lifetime, and a last much-changed one was issued 
eighty odd years after the first publication. 

Stahl (1660-1734) At the close of the seventeenth cen- 
tury chemists began to take up again the views and theories 


of Becher. The greatest chemist of the time was George 
Ernst Stahl. He was born in Bavaria, received a medical 
education at Jena, and was a physician and a professor at 
Halle. He moved later to Berlin, wrote many books, and 
died there in 1734. 

Character and Work. — He was very successful as a teacher, 
gathering large numbers of young men around him as pupils, 
and inspiring them to become investigators. Through them 
he spread his theories. His scientific character was highly 
honorable. He very carefully kept his medicine and his 
chemistry from one another. Though a distinguished physi- 
cian, and the first chemist of his time, he did not attempt to 
fuse the two together. He never sought to carry off the 
honors of others, but gave full credit to all for work done. 
Nor did he hesitate to acknowledge his own errors. In youth 
he maintained that the views of the alchemists were possible 
of fulfilment. In old age he acknowledged their impossi- 
bility, and advised and warned against the pursuit of them. 

His Theory of Combustion. — His theory of combustion 
he states that he derived from the writings of Becher. Cer- 
tainly the latter had very imperfectly stated it, and the most 
of the credit was due to Stahl. He introduced the name 
phlogiston, and extended the ideas as to the nature of this 
combustible principle. Among other things he maintained 
that phlogiston determined the color, and that chemical prop- 
erties were dependent upon it. He presented two views with 
regard to this dependence of chemical properties, one of which 
was true and the other false. 

1. Metals combine with sulphur only so long as they retain 
their phlogiston ; no metal deprived of phlogiston would com- 
bine with sulphur. 

2. No metal deprived of its phlogiston will combine with 
acids. This is true only of ignited oxides. 

General Chemical Work. — Stahl made various additions to 


chemical knowledge. With regard to the question as to the 
relative strength of affinities, which had already engaged the 
attention of several chemists, he prepared lists in which 
the different metals were given in relation to various acids; 
also the order in which a metal at high temperatures was able 
to remove sulphur from a metallic sulphide ; and further the 
acids in relation to the alkalies. 

His knowledge of the acids was more thorough than that 
of any going before him. He recognized sulphurous acid, 
which is produced by burning sulphur alone, as different from 
oil of vitriol, gotten from burning sulphur and saltpetre. He 
improved the method of preparing acetic acid, and was the 
first to show that the concentrated acid would burn. Besides 
these, many other new observations are due to him. In 1697 
he began the publication of the first chemical periodical, under 
the name, " Observationes chymico-pfii/sico-medicce, mensibus 
singulis, bono cum Deo, continua7idce." This soon became a 
purely medical publication and was then discontinued. He 
published several works on chemistry. His lecture notes 
were published by his students under his name. 

Hoffmann (1660-1742). — Friedrich Hoffmann was more a 
physician than a chemist. He held a professorship at Halle 
and afterwards at Berlin, but forty-eight years of his life 
were spent at Halle. It was through him that Stahl was 
Called to Halle, and there was close friendship between the 
two. In general, Hoffmann accepted the views of Stahl, and 
aided in their promulgation. His chemical work was more in 
the line of analyses of mineral waters. Among his achieve- 
ments in experimental chemistry may be mentioned his point- 
ing out the differences between lime, alumina, and magnesia, 
which up to his time had not been clearly distinguished from 
one another. In his qualitative work he set especial store by 
the taste and other physical properties as tests. He intro- 


duced the use of a mixture of equal parts of alcohol and ether 
as an anodyne, and this is still known as Hoffmann's drops. 
He was a prolific writer on medical and chemical subjects. 

Stahl and Hoffmann exercised great influence upon the 
German chemists, and through them the new views as to com- 
bustion were generally introduced. 

Boerhaave (1668-1738). — At the same time a very influen- 
tial figure arose in Holland. Hermann Boerhaave was born 
near Leyden, where he received his education, and became 
professor of medicine and afterwards of chemistry and bot- 
any. The thirty-six years of his residence there were the 
most brilliant in the history of this university. Looking 
at his chemical work alone, we find him distinguished in 
the main as a teacher, and for his skill in interpreting 
chemical facts and the clearness of his theoretical views. 
He exposed the errors of the iatro-chemists, and recognized 
chemistry as a distinct science. 

Overthrow of Alchemical Notions. — He also showed the 
falsity of the views held by the alchemists. He spoke only 
of things tested and observed by himself, and spared neither 
pains nor time to have his observations correct. For instance, 
the alchemists maintained that mercury could be fixed in 
the form of a fire-proof metal, without the addition of any 
other substance. Boerhaave kept mercury at a somewhat 
raised temperature in an open vessel for fifteen years without 
noting any change. So, too, when heated higher in a closed 
vessel for six months, no change could be discovered. This 
convinced him that the fixing of mercury was an impossibil- 
ity. The alchemists said also that if mercury was repeatedly 
distilled, a more volatile essence with peculiar properties could 
be obtained. Boerhaave carried out this distillation five hun- 
dred times without securing the essence. And so he tested 
other of their peculiar notions and prescribed methods with- 


out obtaining the results promised ; and as the methods were 
still credited in some quarters, he did good service in disprov- 
ing them, and won for himself the reputation of being a most 
excellent and painstaking worker. 

Writings. — His lectures were published first without his 
knowledge, and afterwards corrected by him under the title, 
" Elementa Chemice." Repeated editions and translations 
were published in Germany, France, and England. He took 
very little notice of the views and theories of Stahl, though 
these must have been known to him, as they were making 
great headway in Germany. 

Other Phlogistics in Germany The theories of Stahl had 

been pushed and spread by Neumann, Eller, Pott, and others, 
though these had added little to the store of chemical facts 
already known. Marggraf of Berlin was another supporter 
of the Stahl system. He is best known as the discoverer of 
sugar in beets and other garden vegetables, and the first to 
suggest its commercial preparation from them. 


In France, Geoffroy gave voice to views but little different 
from those of Stahl. Helot and Duhamel deserve mention 
also as distinguished French chemists of this time. 

Macquer (1718-1784) The last of the French chemists of 

renown to hold to the phlogistic theory was Peter Joseph 
Macquer, who was born at Paris. He became a member of 
the French Academy at the age of twenty-seven. Excellent 
opportunity for work was afforded him by his position as 
professor at the Jardin des Plantes, and his methods of re- 
search were more like those of the present. He determined 
the solubility of various salts in alcohol, and used this as a 
means of separating them from one another. Some of his re- 


searches were on potassium arseniate, and on the coloring mat- 
ter of Berlin blue. The latter he identified with phlogiston 
because it was destroyed on heating. His great failing was in 
neglecting the quantitative side in his researches. He was 
the author of several text-books, which were highly thought 
of ; but his chief work was his " Dictionnaire de Chimie," 
which appeared first in 1766. This was the first dictionary 
of chemistry, and it was repeatedly enlarged and translated. 


During the latter half of the eighteenth century three 
very distinguished chemists flourished in England, all of 
whom were adherents of the phlogiston theory of Stahl, 
and its most earnest defenders. They were either in ignor- 
ance of, or attached no importance to, the theory of their 
countryman Hooke as to combustion. 

Hooke's Theory of Combustion Hooke's theory, published 

in 1665 in his " Micrographia," claims to be based upon ex- 
periment. It is contained in twelve propositions, but may be 
briefly stated thus : air supports combustion, but this combus- 
tion will take place only after the body has been sufficiently 
heated. There is no such thing as an elemental fire. This 
combustion is caused by a substance inherent in and mixed 
with the air, that is very much like, if not the very same 
with, that which is fixed in saltpetre. If this theory, which 
appeared so many years before the Stahl theory, had been 
accepted, it would have saved much error and a very bitter 

Black (1728-1799) Joseph Black was of Scotch parentage. 

He studied at the University of Glasgow, devoting himself 
especially to physical science. He attended the lectures of 
Dr. Cullen, the most distinguished teacher of chemistry in 


Scotland, and became a co-worker and special friend as well 
as pupil. 

Research upon the Causticity of Lime and the Alkalies. — 
Black first set to work to discover the cause of the differences be- 
tween limestone and lime, and of the causticity of the alkalies. 
The former theory was that lime received its caustic proper- 
ties from the fire with which it was burned, and that it con- 
ferred this upon the alkalies made by means of it. By skilful 
work he showed the part played by carbonic acid in these 
changes. This carbon dioxide he called fixed air, and Black 
is properly regarded as its discoverer. This research, pre- 
pared as his inaugural dissertation for the doctor's degree, 
won for him the professorship at Glasgow, Dr. Cullen having 
removed to Edinburgh. 

Latent Heat and Other Work. — At Glasgow he made the 
brilliant discovery of latent heat, and showed its beneficial 
action in nature. He devoted much time to experiments upon 
heat. James Watt was his pupil and friend. He was most 
successful as a teacher. His writings were few, his manuscript 
lectures being published after his death. Ill-health did much 
to prevent his entering upon the promising field of chemical 
research opened up by his discoveries. He kept up an active 
correspondence with the chief chemists of his day, and exerted 
a widespread influence upon the progress of chemistry. 

Cavendish (1731-1810) An able and eccentric young Eng- 
lishman followed up the work of Black with most gratifying 
success. This was Lord Henry Cavendish. He was born in 
London, his father being a younger son of the house of Devon- 
shire. In early life Cavendish was in very straitened circum- 
stances, and acquired habits of economy or parsimony, and 
certain odd traits which stuck to him through life. After- 
wards he inherited large properties, until he became the largest 
holder of stock in the bank of England. He was exceedingly 


reserved and shy, refraining as far as possible from eommunl 
cations with any save his scientific friends. His education 
was very complete, a thorough training being given him as a 
mathematician, chemist, and afterwards as an electrician. 
His literary labors consisted of eighteen papers published in 
the Philosophical Transactions of the Royal Society. Ten of 
these treat of chemical subjects. 

Discovery of Hydrogen. — His most important work was the 
discovery of hydrogen, which he called inflammable air. This 
he distinguished from the fixed air of Black, concluding that 
this inflammable air was the unaltered phlogiston of the 
metals. He was the first to attempt to determine the specific 
gravity of the gases. He showed that lime carbonate ~was 
held in solution in water by dissolved fixed air or carbonic 
acid. He showed in his experiments on air that when hydro- 
gen was burned water was formed, thus really determining the 
composition of water, though he did not recognize this fact. 
This led to a sharp controversy as to the phlogistication of 
the air or atmosphere, and in the hands of that great inter- 
preter of results, Lavoisier, did much to clear up and advance 
chemical theory. 

Analysis of the Atmosphere. — Cavendish also determined 
by analysis the composition of the atmosphere after oxygen 
had been discovered, and, further, the composition of nitric 
acid. His discoveries practically overthrew the phlogistic 
theory, though he failed to interpret them aright, and re- 
mained a steadfast adherent of the theory. To most fair- 
minded men the theory had been overthrown in 1786 ; and 
yet, until his death in 1810, he refused to give up his belief. 
He preferred to give up chemistry altogether, and devoted 
the later years of his life, in the main, to electricity. 

Priestley (1733-1804). — Joseph Priestley was born near 
Leeds, and received his education at a public school and at ;,n 


academy of the Dissenters. His studies were theological in 
character, and he became a dissenting minister. He was not 
a success in this work, becoming extremely unpopular even 
with his own sect. He also conducted a school, but was in 
very needy circumstances. He was able, however, to buy a 
few books and some instruments, as a small air-pump, an 
electrical machine, etc., and was tireless in his work, training 
himself and his scholars in natural science. Meeting Dr. 
Franklin in London, he was attracted to the study of electri- 
city, and wrote a history of electricity. This, together with 
some new experiments on electricity performed by him, won 
some outside reputation and his election as Fellow of the 
Royal Society. 

Invention of the Pneumatic Trough. — He moved to 
Leeds, settling near a brewery. This gave him opportunity 
for examining the fixed air discovered by Black, and which 
had been shown to be one of the products of fermentation. 
He collected this gas from the vats, and performed many ex- 
periments with it. Moving away from the brewery, he had to 
prepare the fixed air for himself ; and this led to his devising 
the simple and useful pneumatic trough as we now have it, 
and without which we should be very much at a loss in 
experimenting with gases. 

Emir/ration to America. — After staying six years at Leeds, 
he came under the patronage of the Earl of Shelburne, and 
travelled with him through Holland, France, and part of 
Germany. He was very fond of controversial writing, and 
became the object of dislike and attack on the part of those 
with whom he differed. In the heated times of the French 
Revolution, his church and dwelling-house were mobbed and 
burned, his library and apparatus destroyed, and he himself 
escaped with difficulty to London. He was here treated very 
badly by his former associates and others, and finally took 
refuge in America, where he settled in Pennsylvania. In 


this country he pursued his scientific experiments, discovering 
carbon monoxide. He died in retirement in the year 1804. 

Character of his Work. — Priestley was a brilliant investi- 
gator, performing many most striking experiments. He was, 
however, not thorough nor very careful, and was lacking in 
the scientific acumen needed for the proper interpretation of 
his results. It was upon the gases that his most valuable 
work was done ; his invention of the pneumatic trough ena- 
bling him not only to discover new gases, but to investigate 
the properties of many already partially known. 

Discovery of Oxygen. — His method of experimenting is 
well illustrated by his own account of his discovery of oxygen: 
"Having procured a (burning) lens, I proceeded with great 
alacrity to examine, by the help of it, what kind of air a great 
variety of substances would yield, putting them into vessels 
filled with quicksilver, and kept inverted in a basin of the 
same. After a variety of other experiments, I endeavored to 
extract air from mercurhis calcinatus per se ; and I presently 
found that, by means of this lens, air was expelled from it 
very readily. Having got about three or four times as much 
as the bulk of my materials, I admitted water to it, and found 
that it was not imbibed by it. But what surprised me more 
than I can well express, was that a candle burned in this air 
with a remarkably vigorous flame. I was utterly at a loss 
how to account for it." His experiments showed him that 
this air " had all the properties of common air, only in much 
greater perfection ; " and he called it " dephlogisticated air," 
regarding it simply as very pure ordinary air. 

Relation of Plants and Animals to the Atmosphere. — He 
seems to have looked upon all gases as easily changeable, one 
into the other, at least in the first period of his work. Many 
experiments were made by him on the action of the various 
gases known to him upon animals and plants. He would 
place a mouse in a jar of the gas, and notice the effect upon 


its breathing and general life processes. Plants were grown 
in similar jars, and the result upon the growth noted. He 
showed that air which had become noxious through breathing 
or the burning of a candle could be restored to its original 
condition by growing a plant in it. This, he said, was due to 
the impregnation with phlogiston in the first case, and its 
removal in the second. " It is very probable," he says, " that 
the injury which is continually done to the atmosphere by the 
respiration of such a number of animals as breathe it, and the 
putrefaction of such vast masses, both of vegetable and animal 
substances exposed to it, is, in part at least, repaired by the 
vegetable creation." He was unable to explain how this was 

Imperfect Analytical Work. — As an analytical chemist, 
he seems to have possessed little skill. Thus, in his exper- 
iments on the formation of water by exploding mixtures of 
hydrogen and oxygen in a copper globe he obtained a blue 
liquid, whose nature he was unable to determine. The 
analyst whose aid he solicited showed him that it was a 
solution of copper nitrate in water. The fact that nitric acid 
was thus formed induced him to deny that water was a com- 
pound of oxygen and hydrogen. In the hands of Cavendish, 
a more thorough and careful investigator, this discovery led 
to the demonstration of the composition of nitric acid. 

Views as to Combustion. — He held that all combustible 
bodies contained hydrogen. This was, in his view, phlogiston. 
The metals contained it, and their calces, or oxides, were 
simply the metals deprived of hydrogen. 1 Thus, he showed 
that when iron oxide was heated in hydrogen gas the hydro- 
gen was absorbed and metallic iron formed. Rich iron slag 
or cinder was, in his opinion, iron with some hydrogen re- 
tained. To prove this, it was mixed with the carbonates of 
the alkaline earths and heated strongly. This gave him an 
inflammable gas, and all inflammable gases were hydrogen in 
a more or less impure condition, according to his belief. 


Other Researches. — That water could be impregnated with 
carbon dioxide was found out by him, and its use in disease 
suggested. Nitrogen dioxide and carbon monoxide were dis- 
covered by him, but his greatest discovery was that of oxygen 
gas. He examined sulphur dioxide, hydrochloric acid, and 
ammonia in the gaseous form. These are only the most im- 
portant of his discoveries. Inaccurate in his experiments, he 
was decidedly weak as a theorizer. He was a firm believer in 
the phlogiston theory, and endeavored to explain the various 
phemomena noted by him by means of it. 


Sweden, considering her limited area and scanty popula- 
tion, has held a high place as a producer of scientific men. 
This is especially true in chemistry. In the earlier part of 
the eighteenth century, there were several distinguished writ- 
ers upon chemical and alchemical subjects. Among these 
may be mentioned Brandt, Schaffer, and Wallerius. In the 
middle of the century, there was Cronstedt, the great miner- 
alogist ; and the last half of the century produced two great 
chemists, Bergman and Scheele, to be followed by the illus- 
trious Berzelius. The Eoyal Society of Sciences at Upsala 
and the Boyal Academy at Stockholm had much to do with 
this scientific growth. The publications of these two socie- 
ties contained the researches and discoveries of Bergman and 
Scheele, and did much for the progress of chemistry. 

Bergman (1735-1784) Torbern Bergman was born in the 

little town of Katherinaberg. He had the advantages of a 
training at the gymnasium and afterwards at the University 
of Upsala. His family had set him apart for the church or 
for law ; but scientific studies proved a greater attraction for 
him, and he pursued them in secret. He studied mathematics 


especially, and was appointed adjunct professor of chemistry 
in 1761. In 1767 he became professor of chemistry and 
mineralogy, as he had also devoted much time to this study. 
From that time on he devoted every energy to chemistry, and 
his fame soon spread among chemists. Frederick the Great 
endeavored to induce him to go to Berlin, but he preferred to 
remain in his native land. He had many distinguished 
pupils. Hard and continuous application broke down his 
health, and he died in 1784. 

Improvement in Analytical Methods. — His most important 
services were in connection with analytical chemistry. Anal- 
ysis in the wet way, first outlined by Boyle, was still very 
imperfectly understood, and limited mainly to qualitative 
work, and that too upon mineral waters. Bergman enlarged 
the number of re-agents, and studied their action on such sub- 
stances as occur most commonly. Under his guidance analyt- 
ical chemistry began to be an exact science. In quantitative 
analysis he abandoned the plan of isolating the various con- 
stituents, and introduced the methods still used of transform- 
ing each constituent into some compound which could be 
easily isolated, and whose exact composition was known. He 
analyzed a very large number of bodies, examining especially 
into the composition of many salts. Ignorance of the law of 
constant proportions made such work imperfect and unsatis- 
factory. Bergman introduced the method of fusing insoluble 
minerals with caustic or carbonated alkalies, so as to bring 
them into solution, a most important step in analytical 
methods. Some of his researches were masterly and in the 
spirit of the present time. Such, for instance, was his work 
on the differences between wrought iron, steel, and cast iron ; 
also upon the cause of cold shortness in iron. Sweden was a 
great iron-producing country, and this made the work of 
Bergman especially important for his native land. Among 
scientific men he won especial fame by his researches upon 
carbon dioxide and upon affinity. 


Views as to the Atmosphere. — With regard to the atmos- 
phere, he said, " Common air is a mixture of three elastic 
fluids : free aerial acid (carbonic acid), but in such small 
quantities that it does not sensibly alter the color of litmus ; 
an air which can neither serve for combustion nor for the 
respiration of animals, which, therefore, we call vitiated air 
until we know its nature perfectly ; lastly, an air absolutely 
necessary for fire and for animal life, which forms pretty 
nearly the fourth part of common air, and which I regard as 
pure air." In this he was the first to give a clear statement 
as to the composition of the air. This was based on his own 
and Scheele's experiments. 

Theoretical Views, etc. — His theoretical views were in 
accord with those of his age. He regarded hydrogen as 
identical with phlogiston, and accepted in full the phlogistic 
theory. His chemical contributions were numerous ; and be- 
sides these, many papers upon mineralogy, geology, physics, 
astronomy, and zoology were published by him in the 
Memoirs of the Stockholm and Upsala Academies. 

Scheele (1742-1786).— Carl Wilhelm Scheele was a com- 
patriot and contemporary of Bergman, and closely connected 
with him. His educational training was more limited than 
that of Bergman. While engaged as a pharmacist at Gothen- 
burg, he read all the chemical works in his reach, and dili- 
gently experimented so far as his limited means would 
permit. He moved finally to Upsala, and there attracted 
the attention of Bergman ; although there was at first, on the 
part of Scheele, some distrust, arising from their previous 
dealings with one another in regard to one of Scheele's first 
researches. A firm and lasting friendship sprang up be- 
tween the two, helpful to each, and most beneficial to 
science. Scheele remained a pharmacist through life, poor 
and reserved, receiving a small stipend from the Stockholm 


Academy, better known abroad than by his nearest neigh- 
bors, and yet out of his poverty and imperfect appliances 
achieving wonderful success in mastering nature's secrets. 
He died in 1786, when only forty-three years of age. 

His Discoveries. — No one, before nor since his day, has 
made so many important discoveries. In fact, it is only the 
recent publication of his letters which has revealed how much 
he knew, and how far he was ahead of his times. His first 
work was upon the organic acids, many of which he isolated 
and examined. Among organic acids, he discovered tartaric 
oxalic, malic, citric, and gallic acids ; among inorganic, molyb 
die, tungstic, and arsenic acids. Manganese, chlorine, baryta, 
and oxygen were discovered by him. He adhered to the 
phlogiston theory which dominated the age, his chief deficiency 
lying in this matter of generalizing and formulating theories. 

Discovery of Oxygen. — One of his most important discov- 
eries was the constitution of the atmosphere. His work in 
this was distinct from that of Lavoisier and Priestley. He 
examined the atmosphere with a view to determining what 
part it played in the phenomena of combustion. First, he 
examined the action of various substances upon the air. 
These substances were supposed to contain phlogiston, and 
hence, he reasoned, would give it off to the air held in an 
enclosed space. Some of the substances experimented upon 
were moist iron filings, fresh moist iron hydroxide, etc. He 
observed that the air diminished in amount, and that the 
portion left was incapable of supporting combustion. This 
diminution of volume, he reasoned, was due to an absorption 
of phlogiston by the air, hence the air should be specifically 
heavier. To his astonishment, he found the opposite to be 
true. A part of the air had disappeared, and the remainder 
was specifically lighter. Scheele concluded that the atmos- 
phere consisted of two different kinds of air ; one kind having 
no power of taking up phlogiston, and hence being left behind 



in combustions, the other taking up phlogiston in an enhanced 
degree. This was his fire-air, or Lavoisier's oxygen, though 
not yet known to the great French chemist. His experiments 
as to the relative proportions of these two constituents fall 
in accuracy far behind those made a little later by Cavendish. 
He pursued his research further, and was badly misled by the 
phlogiston fancy. Thus, in explanation of the experiment 
just described, he concluded that the union of phlogiston with 
one part of the air caused a diminution of volume, because a 
tenuous, delicate substance had been formed which escaped 
through the pores of the glass vessel. This delicate sub- 
stance was, in his opinion, fire or heat. Fire, then, was a 
combination of fire-air and phlogiston. This fire or heat, he 
believed, could be decomposed into its constituents by the use 
of such substances as would combine with the phlogiston, and 
set the fire-air free. He thought he could do this with nitric 
acid. He distilled nitre and oil of vitriol, and obtained nitric 
acid and a gas which supported combustion better than the 
air itself. 

This supposed decomposition of heat he effected further 
by heating other substances, as manganese dioxide, and nitre. 
Thus he isolated oxygen, or, as he called it, fire-air. 

Theoretical Conclusions. — The theoretical conclusions 
reached by him from a number of experiments were : — 

1. That phlogiston was a true element. 

2. That by the affinity which it had for certain sub- 
stances it could be transmitted from one body to another. 

3. That it combined with fire-air to constitute caloric or 

4. That this heat, in the case of its formation from com- 
bustion, or by respiration, adheres to the corrupted air (nitro- 
gen), and renders it lighter. 




The great chemists whose lives we have just given were 
the most distinguished exponents of the phlogiston theory and 
its last noteworthy defenders. We come now to one of the 
most illustrious of chemists, through whose labors a great rev- 
olution in chemistry was wrought, and the theory of phlogiston 
overthrown. So great were his services to chemistry that his 
countrymen seem almost justified in styling him the Father of 

Lavoisier (1743-1794) Antoine Laurent Lavoisier was born 

in Paris. No expense was spared in his education ; and he 
made rapid progress in acquiring knowledge, especially of the 
sciences. At the age of twenty -one, he obtained a medal from 
the government for a memoir upon the best and most economi- 
cal method of lighting the streets of a large city. This was 
a competitive prize, and in this early piece of work he showed 
the same painstaking care and accuracy which distinguished 
him in after life. He is said to have lived for six weeks in 
rooms lighted by artificial light, so as to accustom his eyes to 
the slight differences in light for the purpose of his investiga- 
tions. He was chosen an adjunct member of the French 
Academy at the unusually youthful age of twenty-five; and 
from that time on the memoirs of the Academy were enriched 
by his contributions, and he became one of its most important 



members and officers. Chemistry did not receive the whole of 
his attention at first, but shared it with geology, mineralogy, 
and mathematics. The wonderful discoveries in chemistry, 
especially pneumatic chemistry, which were being made known 
by Black, Priestley, Scheele, and others, drew him, how- 
ever, to devote all his energies to scientific chemistry. For 
more than twenty years he was indefatigable as a worker, re- 
peating the experiments of others and pursuing fresh lines of 
inquiry. By good business management he greatly added to 
his property and became a man of wealth. He lived well, 
giving dinners which were famed for their excellence and for 
the company gathered at them. This drew attention to him 
as a man of wealth, and won for him some enemies whose in- 
fluence was felt in the storm gathering against all that smacked 
of aristocracy. Besides, he was a fermier-g 'eneral ; and, though 
he brought about some reforms, some of his measures proposed 
to the government were exceedingly unpopular, as, for instance, 
his plan for taxing Paris. His scientific knowledge was 
turned to the service of the state, and he improved the nitre 
factories and the manufacture of gunpowder. When the revo- 
lution succeeded, and Paris was under the control of Robes- 
pierre, the Dictator, he was thrown into prison along with 
others who had been farmers of the revenue. The palpably 
ridiculous charge of " adulterating the tobacco with water and 
other ingredients hurtful to the health of the citizens " was 
brought against him and sufficed for his conviction. Appeals 
in his behalf, on account of his learning and his usefulness, 
were vain. The judge replied to all such appeals, " We have 
no need for savants." 

He was guillotined in the year 1794, at the age of fifty-one; 
and France and the world lost one of the clearest intellects 
and most comprehensive minds that science has known. 

Character of Ids Work. — Lavoisier's most valuable ser- 
vices were as an interpreter of the results of his own work 


and that of others. He showed a marvellous insight into the 
causes of things, a quick perception of the importance of the 
many discoveries of his times, and a comprehensive grasp of 
facts and their inter-relation and connection. These powers 
enabled him to detect the errors and falsity in the theory and 
reasoning of the chemists of his age, and to lay the basis for 
the new chemistry of the quantitative era. Exclusive impor- 
tance had been attached hitherto to visible phenomena, whereas 
he introduced a deeper study of chemical reactions and the 
relations of quantity. 

Experiments upon Combustion. — In 1774 he published his 
first strictly scientific volume under the title of "Essays 
Physical and Chemical." In this he described all that had 
been done on the subject of gases, from the time of Paracelsus 
down through the work of Priestley. He further gave an 
account of his own experiments. He showed that when metals 
were calcined their weights increased, and that a portion of 
air, equal to their increase in weight, was absorbed from the 
surrounding atmosphere. He burned phosphorus in the air, 
and observed the decrease in the volume of air and the increase 
in weight of the phosphorus. We are apt to think that the 
mere proof that the metallic calx weighed more than the metal 
was sufficient to disprove the phlogiston theory. But both 
parts of the proof of Lavoisier were necessary ; and even then 
it was insufficient, merely preliminary to his final work. It 
had long before been shown that the calces were heavier than 
the metals from which they came, and that they were specifi- 
cally lighter. The phlogistics, however, thought these weight 
relations of little importance, claiming, in fact, that the pres- 
ence of phlogiston added nothing to the weight of a body but 
made it specifically lighter. 

Composition of the Atmosphere. — In his first book, he 
tells of nothing to show that he knew the composition of the 
air or the distinct nature of oxygen. They were discoveries 


reserved for Scheele and Priestley, but Lavoisier was evidently 
very near to their discovery, and was only anticipated in this 
work by these eminent investigators. When Priestley visited 
Lavoisier shortly afterwards, and showed him how to prepare 
oxygen from the red oxide of mercury, Lavoisier immediately 
saw what the discovery meant, and how it made plain much 
that was unexplained in his own work. It altered his views, 
and suggested to him the nature of atmospheric air, and of the 
changes taking place in the calcination of the metals. For 
twelve years he worked over these problems, performing a 
great number of experiments and with an accuracy hitherto 
unknown. He then boldly proclaimed the non-existence of 
phlogiston, and replaced this old theory by a new one, explain- 
ing the phenomena of combustion and reduction as combination 
with oxygen, or its separation. He first won to his views the 
distinguished French chemists of his day ; and before many 
years all men of standing in the science gave in their adher- 
ence to his new theory, except a few who could not give up 
views which had formed the basis of all their scientific work. 
The year 1786 may be fixed as the one in which the death- 
blow was given to the phlogiston theory. 

Professional Character. — Besides these volumes of essays, 
Lavoisier was the author of a treatise on chemistry and of 
about sixty memoirs published by the Academy of Sciences. 
It must be said that it seems that Lavoisier did not always 
show strict ideas of personal honor and uprightness in giving 
credit to others for their discoveries and work. This was 
notably the case in his tacit claim to the discovery of oxygen, 
although Priestley had shown him the method of preparation 
in the year previous to the publication of his memoir. 

Composition of Water. — One of his most important me- 
moirs was upon the composition of water, and it was this 
research which gave him his complete triumph over the sup- 
porters of the phlogiston theory. The hydrogen evolved when 


a metal was dissolved in an acid was held to be identical with 
the hypothetical phlogiston, and this reaction was the last 
argument brought forward in support of that theory. When 
Cavendish's discovery of the formation of water by the burn- 
ing of hydrogen was told to him, Lavoisier saw his way to a 
solution of this puzzle, and lost no time in repeating so im- 
portant an experiment. He claimed that the hydrogen 3ame 
from the water, which took part in the reaction ; at the same 
time the oxygen was fixed in the metal, and thus it was not 
the metal, but the metallic oxide, which was dissolved up by 
the acid. In other cases, as in the action of nitric acid upon 
copper, the metal decomposes the acid and not the water, 
taking oxygen from it to form an oxide, and this is dissolved 
by the remainder of the acid. The deoxidized part of the 
acid escapes as a gas. ' 

Theory as to Acids. — Thus he recognized the parts played 
by oxygen in the formation of acids, of oxides, and of salts. 
For these he gave the simple definitions which form the 
foundation of the new chemistry. 

1. An acid results from the union of a simple body, ordi- 
narily non-metallic, with oxygen. 

2. An oxide is a compound of a metal and oxygen. 

3. A salt is formed by the union of an acid with an oxide. 

This theory was extended farther for the sulphides, phos- 
phides, etc., but the true nature of the chlorides was not 

Transmutation of Water Refuted. — One of Lavoisier's 
earlier memoirs (1770) well illustrates his accuracy, thorough- 
ness, and acute reasoning. It had been noted by many earlier 
investigators, that when water was boiled for a long time in 
a glass vessel, a mass of white residue was found in the vessel 
after evaporation. This was long regarded as a conclusive 
proof that water could be changed into earth. Lavoisier 
weighed his glass vessel, and then, after heating water therein 


for one hundred days, found there was no change in the weight 
of the vessel and its contents. When he evaporated the 
water he got a residue of earthy matter which he found cor- 
responded, within the range of experimental error, with the 
loss in weight of the empty vessel. He therefore concluded 
that water on being boiled is not changed into earth, but that 
a part of the matter of which the glass is composed is dis- 
solved out by the water ; and the analytical work of Scheele 
afterwards showed that this residue did have the same com- 
position as the glass, thus confirming the work of Lavoisier. 

Indestructibility of Matter. — The old alchemical notion of 
transmutation was thus shown to be false, and was finally 
dismissed from chemistry. Lavoisier established the impor- 
tant generalization that matter may be changed, but not de- 
stroyed nor created. The matter lost from the glass vessel 
was merely dissolved in the water. This is the principle 
of the Indestructibility of Matter, the fundamental principle 
of modern science. Of course Lavoisier's work was only the 
beginning of the series of experiments on this subject which 
after many years established the principle. 

The Relation of Plants and Animals to the Atmosphere. — ■ 
Priestley had performed various experiments upon the gases 
or airs known to him ; and, as has been said, had discovered 
the relation of the plants and animals to the atmosphere, and 
the approximate balance maintained by their action upon it. 
His ignorance of accurate analytical work and his devotion 
to the phlogiston theory prevented his reaching a true ex- 
planation of the facts observed by him. Lavoisier and 
Scheele determined the composition of the atmosphere, and 
afterwards Cavendish gave an exact analysis of it. Lavoisier 
had shown that it consisted of oxygen and nitrogen, and had 
determined the proportions of each. He was therefore in a 
position to complete and explain the work of Priestley. The 
processes of breathing and of calcination were chemically 


analogous. Oxygen was drawn into the lungs by the respira- 
tion of animals ; there it combined with carbon, and the car- 
bonic acid, or the hxed air of Black, was breathed out. This 
was noxious to other animals, and this it was which was 
removed by the plants. These experiments serve well to 
show the confusion of thought of the phlogistics, and the 
clearness of Lavoisier's methods. 

Vieivs as to the Nature of Heat and of Matter. — Lavoisier 
disproved the old ideas as to the elemental nature of heat, 
yet he believed it to have material existence. He writes of 
a matiere de chaleur, which he also calls calorique. He as- 
cribed to it a fluid nature, but said that it had no weight. 
His idea, and also his views upon the constitution of matter, 
are perhaps best given-by a citation from his "Reflexions sur 
le Phlogistique." Matter, he says, consists of small particles 
which do not touch one another, otherwise the diminution 
in volume on cooling could not be explained ; between these 
particles is the calorique. In gases there is most of this ca- 
lorique, in solids least ; and in his experiments with Laplace 
upon specific heat, he has shown that solids differed in their 
capacity for taking up this heat. His views are in partial 
agreement with the modern theory of heat, when he comes to 
define that form of energy. He says, " Heat is the result of 
invisible motion of the particles, the sum of the product 
of the masses multiplied by the square of the velocities." 
We may say that he laid the foundation for the modern 
therm o-chemistry. 

Investigation of Organic Substances. — Lavoisier also occu- 
pied himself with organic chemistry, or the chemistry of life- 
products, and made a beginning towards a scientific study of 
it by devising a method of analysis by which these bodies 
could be burned, and the water and carbon dioxide which were 
formed measured. Of course such a system of analysis was 
impossible until the composition of these bodies themselves 


was definitely fixed. That these bodies, as well as carbon (in 
imperfect combustions), were gotten on burning organic sub- 
stances had been long known ; but their nature, and the ques- 
tion of their pre-existence in these substances, had been the 
subject of endless discussions. Through his analyses, Lavoisier 
determined that all organic substances were composed of car- 
bon and hydrogen, sometimes oxygen, and less often nitrogen, 
sulphur, and other elements. 

Chemical Nomenclature. — The nomenclature of chemistry 
was in a most unsettled and unsatisfactory condition at this 
time. Many of the terms used were abused, and many un- 
wieldy ; and throughout all there was a coloring from phlo- 
gistic ideas and a lack of system. It was impossible for 
Lavoisier to express his ideas clearly and intelligibly, or to 
put the new chemistry into such language ; and hence he joined 
with Guyton de Morveau in simplifying and systematizing the 
terminology. The new system came into use very rapidly 
because of its great superiority. Of course it was inadequate 
to supply fully the needs of later times, but it forms the basis 
of our present system, 


The overthrow of the followers of Stahl, and the accept- 
ance of Lavoisier's ideas, ushered in a new era in chemistry. 
A new nomenclature was needed, and it was created by 
Lavoisier and the Trench Encyclopaedists. Changes in the 
theories as to acids and bases were demanded ; and Lavoi- 
sier gave them, at least in outline, to be filled up and 
modified afterwards as knowledge increased. These theories 
were not in every point correct, but they were far nearer to 
the truth than any which had preceded them. The name of 
oxygen, or acid-producer, which Lavoisier gave in 1778 to what 
was at first called dephlogisticated air, is a perpetual reminder 
of his theory, even though that theory was only partly true. 


The Elements. — But the most striking and far-reaching 
change was in regard to the elements, a name to which chem- 
ists had not attached very much importance up to this time, 
and which was rather hazily defined. They had been hitherto 
mainly the subject of philosophical speculations. Hencefor- 
ward they were to form the basis of systematic chemistry. 
The four-element theory of Empedokles and Aristotle was a 
dream, a philosophical figment, without basis or confirmation 
in experiment. These elements were regarded as principles, 
with certain material characteristics, entering, all or some of 
them, into every known substance, and not necessarily capable 
of independent existence themselves. Some chemists, indeed, 
undertook to prove that certain substances did contain these 
principles ; as, for instance, when green wood burns, flame 
showed the existence of fire, the ascending smoke proved the 
presence of air, the hissing and boiling gave abundant evidence 
of water, and the remaining ashes vouched for the last element, 
earth. There was no attempt at a general proof, but the alche- 
mists seem to have accepted the theory of Aristotle down to 
Boyle's publication of his "Sceptical Chymist" (1661). Boyle 
was in error in believing that one substance could be changed 
into another, as, for instance, that water could be transformed 
by prolonged boiling into earthy substances ; but he undoubt- 
edly overthrew the doctrine of elementary principles as held 
by those whom he styled " vulgar chymists." 

He defined elements as " certain primitive and simple bodies, 
which, not being made of any other bodies, or of one another, 
are the ingredients of which all those called perfectly mixed 
bodies are immediately compounded, and into which they are 
ultimately resolved." He did not believe himself warranted, 
by the knowledge then possessed, in proclaiming the positive 
existence of such elements. It is true that Van Helmont had 
previously rejected the Aristotelian theory, at least with regard 
to fire, and had antagonized the ideas of the alchemists spring- 


ing from Geber's hypothetical elements, mercury, sulphur, and 
salt. Still, he held on to water as an element, and did not 
have Boyle's clearness of vision regarding this matter. 

During the phlogistic period, less and less importance was 
attached to the old ideas as to elements ; and the belief gradu- 
ally sprang up that a true element must be something which 
could be prepared, and which was not subject to change. 
Macquer, in his Dictionary of Chemistry (English translation, 
1777), gives the modern definition, worded as follows: "Those 
bodies are called elements which are so simple that they 
cannot by any known method be decomposed or even altered, 
and which also enter as principal or constituent parts, into the 
combination of other bodies, which are therefore called com- 
pound bodies." But he adds, " The bodies in which this 
simplicity has been observed are fire, air, water, and the 
purest earths." Black proved that certain chemical sub- 
stances were possessed of a constant and definite composition 
and fixed properties, unalterable, and hence simple bodies or 
elements. Lavoisier, in his " Traite de Chimie," enunciated 
the definition of an element which is in accord with our pres- 
ent knowledge and beliefs. " An element is a substance from 
which no simpler body has as yet been obtained ; a body in 
which no change causes a diminution of weight. Every sub- 
stance is to be regarded as an element until it is proved to be 
otherwise." With these clear definitions to build upon, a 
rational system of chemistry became for the first time a possi- 
bility. It is true that many substances were classed as ele- 
ments which did not belong to the list. It is very possible 
that the same may be the case even now. Lavoisier first 
classed the metals as elements. 

Spread of the New Chemistry The teachings of Lavoisier, 

or as Fourcroy styled it, the "French Chemistry," speedily 
found acceptance in France, in England, and through the in- 


fluence of Klaproth, in Germany, among Stalil's own country- 
men, where the opposition had been intense. By the close of 
the century chemists had almost universally given in their 
adherence to the new doctrines. 

Chemistry now had the basis of a true theory ; and what 
was of greater value, a knowledge that theories could be 
deduced only from the weight relations of actually occurring 
reactions. There were to be no baseless and delusive dreams 
for the future, although mistakes might be made in the inter- 
pretation of facts. Further, the grand division into elements 
and compounds had been effected, and a suitable nomenclature 
had been devised, capable of any expansion demanded by 
increase of knowledge. The balance, too, had been introduced 
as the instrument by which precision and accuracy were to be 
attained, and the great arbiter of the fate of theories. True 
progress now became possible ; and the century which has 
since passed has seen this science develop and grow, until men 
have come scarcely to dare to put a limit to its possibilities. 

In the latter part of the eighteenth century, it grew to be 
the fashion for ladies and gentlemen of rank, in large numbers, 
to attend the lectures of distinguished chemists. Thus 
Scheele entertained the Crown Prince of Prussia, and people 
of note crowded the lectures of Fourcroy and Lavoisier. An 
army of workers sprang up, and facts almost innumerable 
were added to the store. The succeeding history differs from 
that which has preceded largely in this, that the lives and 
achievements of individuals can no longer suffice to give us 
an idea of the growth of the science, and must occupy small 
space in these pages. 

Still, we find that, though facts rapidly increased in number, 
theories were slowly evolved, and gained acceptance only after 
most careful weighing and testing in every known way. In 
this respect the experience of the past was invaluable. Great 
names, so-called authorities, might gain a hearing for a 


theory, but could never again secure recognition for it. Men 
had cast off forever the burden of authority in science. The 
work begun by Paracelsus was complete. 


The ground-work of the new chemistry was laid by 
Lavoisier, in the following dicta: — 

1. In all chemical reactions, only the form of the mate- 
rials changed, the quantity remained the same. The sub- 
stances used and the products gotten can be brought into an 
algebraic equation, by means of which any one unknown 
member may be calculated. 

2. In all combustions the burning body unites with 
oxygen ; and in general an acid is formed by combustions of a 
non-metal, and, by combustion of the metals, a metallic calx 
or oxide is formed. 

3. All acids contain oxygen united with a base or a radical 
which, in the case of inorganic bodies, is generally an element ; 
in organic, it is made up of carbon and hydrogen, and often 
contains nitrogen and phosphorus, as well as other elements. 

The Constancy of Proportions With regard to the ques- 
tion whether chemical compounds are possible with all pro- 
portions of the constituents, or whether bodies can combine 
only in certain definite proportions, Lavoisier took the latter 
view ; and this was generally accepted, although there was no 
direct general proof of its truth. But in 1803, Berthollet, in 
his " Statique Chimique," denied that compounds were formed 
only in certain definite proportions. 

Berthollet (1748-1822) Berthollet was, after the death 

of Lavoisier, the leading French chemist. His most impor- 
tant chemical work was in connection with the composition of 



ammonia, the properties and nature of chlorine, and the man- 
ufacture of bleaching compounds from it. His work in con- 
nection with hydrogen sulphide and hydrocyanic acid was of 
deep theoretic interest, and proved of great value in arriving 
at the true theory of acids. His greatest service to the 
science was in the publication of his " Essai de Statique 
Chimique." This book excited a great deal of discussion 
among chemists, and was a most important contribution to 
chemical literature and theory. It contains much that is true, 
as Berthollet took the principles of mechanics and physics as 
the basis for his study of chemical reactions. Some of his 
deductions and inferences have been proved wrong, but there 
is truth in a good deal he has written. 

Views of Affinity The work is especially directed against 

false views of affinity and the misuse of the so-called affinity 
tables which had been drawn up by many chemists. As 
specimens of such tables, those of Geoffroy and Bergman may 
be given : — 

geoffroy's table. 

Hydrochloric Acid 


Fixed Alkali 


Fixed Alkali 

Sulphuric Acid 



Nitric Acid 



Hydrochloric Acid 



Acetic Acid 








In this table, as one goes down the first column, for 
instance, each substance has a weaker affinity than the one 
just preceding it for hydrochloric acid ; and so for the other 

Bergman's is very similar. He gives the affinity of 
various substances for sulphuric acid, as determined by his 


experiments. The table shows a knowledge of the fact that 
the affinity depended upon the temperature and the physical 

Bergman's table. 


Baryta Phlogiston 

Potash and Soda Baryta 

Ammonia Potash 

Alumina Soda 

Zinc oxide Lime 

Iron oxide Magnesia 

Copper oxide Metallic oxides 

Mercury oxide Ammonia 

Silver oxide Alumina 

Berthollet's work has exerted a lasting influence upon the 
views concerning affinity, and shows in high degree the power 
of abstract conception and of logical development of chemical 
ideas on the part of this, the first and ablest of Lavoisier's 
followers. He reasoned that affinity was by no means a 
simple force, and easy to determine or measure ; but was 
influenced by temperature, physical state, cohesion, and espe- 
cially by mass. The latter largely determined the course of 
chemical reactions. He went further, and stated that the 
mass of the combining bodies determined the proportions in 
which they would unite to form compounds. 

His views as to the lack of any fixity or constancy of pro- 
portions in chemical compounds met with immediate opposition 
on the part of leading chemists, and gave a new direction to 
their researches. The absorbing object of search became 
the exact quantitative composition of the compounds known, 
so that, based on such knowledge, a true hypothesis might be 

Dalton (1766-1844) Among these workers was the Eng- 
lishman, John Dalton, the author of the atomic theory. It is 


interesting to note how Dalton's work led up to this great 
fundamental idea of modern chemistry. He was a mathema- 
tician and physicist, and for years had been interested in 
meteorological observations. His observations upon dew and 
upon aqueous vapor existing in the air led him to the publi- 
cation, in 1801, of an important paper upon the " Constitution 
of Mixed Gases, etc." This was followed by other papers on 
the properties of gases, and they prove that he had formed 
the idea that gases were made up of small distinct particles. 
He speaks of the pressure on them, the repulsion between 
these particles, and says, " A vessel full of any pure elastic 
fluid (gas) presents to the imagination a picture like one full 
of small shot." In considering the question as to why water 
does not mechanically dissolve the same bulk of every gas, he 
says : " I am nearly persuaded that this circumstance depends 
upon the weight and number of the ultimate particles of the 
several gases, those whose particles are lightest and single 
being least absorbable, and the other more, accordingly as 
they increase in weight and perplexity. An inquiry into the 
relative weights of the ultimate particles of bodies is a sub- 
ject, as far as I know, entirely new." He gives in this paper 
(1802) a " table of the relative weights of the ultimate par- 
ticles of gaseous and other bodies." These views of Dalton 
attracted widespread attention and discussion, which Dalton 
welcomed, because he believed that " the truth will surely 
out at last ; " and it was the truth that he aimed at. Dalton 
was often inaccurate as to facts, deficient in the details of 
chemical manipulation, and did not hold high rank as an 
experimenter; but he was good at drawing conclusions, and 
at stating generalizations, his aim being the establishment of 
general, underlying laws. 

Atoms Of course the idea of the existence of atoms was 

not new nor original with Dalton. The conception of the 


Greek philosophers was that " The bodies which we see and 
handle, which we can set in motion or leave at rest, which we 
can break in pieces and destroy, are composed of smaller 
bodies which we cannot see or handle, which are always in 
motion, and which can neither be stopped, nor broken in pieces, 
nor in any way destroyed or deprived of the least of their 

Now, something of this conception was held and felt 
all through the earlier days of chemistry. The physicists, 
Newton and Bernouilli, held it, the latter believing the pres- 
sure exerted by a gas upon the enclosing walls to be due to 
the constant bomhardment of the atoms. We have seen how 
this idea was present in the mind of Lavoisier. It was then 
in the air, as it were, a dream, a fancy of the philosophers, 
without tangible proof, yet often incorporated in their views 
and theories. The credit which belongs to Dalton is that he 
took this dream, and, by means of collected facts and laws, 
gave it that confirmation which was necessary in order that it 
might be ranked as a theory. 

Proust (1755-1826) Most important aid was rendered 

Dalton in his work by the skilful and careful analytical labors 
of Proust, a countryman of Berthollet, and a strong opponent 
of his views. In fact, Proust very nearly anticipated Dalton 
in his discovery of the law of multiple proportions, which gave 
most support to the atomic theory. 

Proust entered upon a brilliant defence of the law of 
constant, or definite, proportions, which had been partially 
established by the work of Lavoisier and Vauquelin, and which 
was now attacked by Berthollet. The interchange of letters 
between Proust and Berthollet lasted during eight years, and 
attracted the attention of all chemists. These were not mere 
theoretical disquisitions, but recounted the experiments and 
counter-experiments of the authors, and many new facts were 


brought out by them. Berthollet lost most of his adherents 
before the close of the controversy. One of the good results 
of this controversy was to bring about a definition of com- 
pounds and mixtures, and a clear distinction between them. 
In the course of it, also, Proust discovered the hydroxides, a 
class of compounds until then confused with the oxides. 

Richter (1762-1807) Another earnest supporter of the 

law of definite proportions was Kichter, though probably his 
work was unknown to Dalton. He published (1792-1794) the 
results of his work upon the proportions by weight in various 
compounds, under the title of "A Foundation for the Stoichi- 
ometry, or Art of Measuring Chemical Elements." This is 
the first work on systematic quantitative analysis. It was 
a decade or more before Eichter's excellent work received 
appropriate recognition. 

Law of Multiple Proportions. — So the idea of the fixity of 
proportions became firmly incorporated in the science, and we 
can speak of it as a recognized law. With this proved, it 
needed but one step more to give a sure basis for Dalton's 
theory of the existence of atoms. When Dalton discovered 
the Law of Multiples, or, in other words, when he found that 
if two elements combined to form one compound, there were 
certain definite proportions in which they united, if they 
formed more than one, then the proportions progressed by 
regular increments, an increase of once or twice the first 
proportion, or of some simple multiple of it, he saw that his 
hypothesis of atoms gave a plausible, and the only plausible, 
explanation of these facts. 

The Atomic Theory and its Extension Dalton told his 

theory to Thomson ; and he published Dalton's views in his 
" System of Chemistry," in 1 807. Sir Humphry Davy opposed 
this new hypothesis, but was won over to it, and so were Wol- 


laston and others, though they saw difficulties in its application 
which greatly delayed its general acceptance. 

The essential parts of Dalton's theory can be put in two 
sentences. 1. Every element is made up of similar atoms of 
constant weight. 2. Chemical compounds are formed by the 
union of the atoms of the different elements in simple numer- 
ical relations. 

His speculations as to the form of the atoms, declaring 
them to be spherical, and that they did not touch one another, 
are of subordinate importance, and had little to do with the 
after development of the theory. 


If the atomic hypothesis was a true explanation of the 
facts of chemical combination, then its iirst and most impor- 
tant application would lie in a determination of the relative 
weights of the atoms of the various elements. This might be 
arrived at by a determination of the combining proportions 
entering into different compounds, provided the number of 
atoms in such compounds were known. Now, it was in this 
that the supporters of the theory met their hrst and greatest 

Dalton's Rules for Determining Atomic Weights Dalton 

began to determine the weights of the atoms, taking as his 
standard hydrogen. A list of these weights determined by 
him was published as early as 1805. They show very faulty 
analytical work, and were entirely superseded by the later 
classical work of Berzelius. In fact, they seem to have come 
very slightly into use. To overcome the difficulty of telling 
how many atoms entered into combination to form a particle 
of any compound, he adopted certain very arbitrary rules, 
which were afterwards shown to be without just basis. These 


rules have the merit of simplicity, however, and were about 
the best that could be formulated at that time. First he di- 
vided compounds into binary, ternary, quaternary, etc., accord- 
ing as they contained two, three, four, or more atoms. Then 
he adopted the following rules : — 

1. When only one combination of two bodies can be ob- 
tained, it must be presumed to be a binary one, unless some 
cause appear to the contrary. 

2. When two combinations are observed, they must be 
presumed to be a binary and a ternary. 

3. When three combinations are obtained, we may ex- 
pect one to be a binary and the other two ternary. 

4. When four combinations are observed, we should ex- 
pect one binary, two ternary, and one quaternary, etc. 

Besides this difficulty, Dalton's use of the term atom was 
confusing. He made no distinction between the ultimate par- 
ticles of elements, or of compounds, or the ideal indivisible 
atom. This was a most serious flaw. It caused Dalton him- 
self to reject the work of Gay Lussac ; and it caused others to 
hesitate to accept Dalton's views, seeing these inconsistencies. 
Two things were much needed : a clearer definition of atoms, 
and some reliable method of determining the number of atoms 
in a compound particle. 

Gay Lussac (1778-1850) The latter problem was partially 

solved by the labors of Gay Lussac. This distinguished pupil 
of Berthollet was a trained chemist, capable of the most accu- 
rate analytical work, and possessing scientific acumen in a 
very high degree. He enriched chemical literature with 
many excellent researches, working often in company with 
Thenard, Humboldt, and Liebig. His most noteworthy work 
was upon iodine, cyanogen (the first compound radical), the 
alkaline oxides, the isolation of boron, improved methods for 
organic analysis, and many similar studies. 


The Law of Volumes. — But his name is especially asso- 
ciated with his researches upon combining volumes of gases. 
He discovered the law of the expansion of gases under the 
influence of equal temperatures. He also studied the combin- 
ing volumes of gases, and deduced from his experiments the 
Law of Volumes. This law of volumes may be stated thus : 
the volumes of combining gases bear a simple ratio to one 
another and to the volume of the resulting gaseous product. 
This law was announced by him in 1808. 

Difficulties and Objections. — Gay Lussac was well ac- 
quainted with Dalton's hypothesis, and showed in part how 
his discoveries accorded with it. A similar molecular condi- 
tion was essential in order that all gases should behave alike 
towards pressure and changes of temperature, and, besides, 
obey his law of volumes. In other words, equal volumes of 
gases must contain equal numbers of molecules. Gay Lussac 
made no distinction between these molecules and atoms, re- 
cognizing but one kind of final particle. Dalton took excep- 
tion to this reasoning, and in his reply said that he too had 
once held the same idea as to combining volumes, but had 
seen that it was untenable. He further maintained that the 
experiments of Gay Lussac were inaccurate, and that the 
gases did not combine exactly by volumes, but often by frac- 
tions of volumes. His argument can be illustrated best by 
taking some substance, as hydrochloric acid, as an illustration. 
One atom of hydrogen chloride consists of one atom of hydro- 
gen and one atom of chlorine. Now, if equal volumes of 
gases contain equal numbers of molecules, one volume of 
hydrogen and one volume of chlorine should give one volume 
of hydrogen chloride, but they really form two. Therefore 
each one of these can contain only half as many atoms as the 
original volumes of the constituents. This reasoning is mani- 
festly final so far as the theory of the volumes containing the 
same number of atoms is concerned, unless some different 
definition of atoms is assumed. 


Avogadro's Theory The solution of the difficulty was 

shown by Avogadro. This Italian physicist made a distinc- 
tion between what he called molecules integrantes and mole- 
cules elementaires, or, as we may translate the terms, molecules 
and atoms. The molecules were compound particles, and were 
made up of the indivisible atoms. The researches of Gay 
Lussac show, then, that a molecule of water consists of one 
molecule of hydrogen and one-half molecule of oxygen. A 
molecule of hydrogen chloride consists of one-half molecule of 
hydrogen and one-half molecule of chlorine, and so the diffi- 
culty pointed out by Dalton disappeared. 

Avogadro also pointed out how this law of volumes 
enabled one to determine the number of atoms in a molecule 
of a gaseous compound, whereas the rules of Dalton were 
purely arbitrary. He went farther, and determined the num- 
ber of atoms in the molecules of various elements. 

Ampere. — These discoveries of Avogadro are often credited 
to the French physicist, Ampere; but his memoir appeared 
three years later (1814), and lacks the clearness and fulness 
of that of Avogadro. His memoir first appeared in the form 
of a letter to Berthollet, and he showed in it his ignorance of 
Avogadro's work. The views of these two did not have an 
immediate effect upon the chemical world ; and, indeed, a half 
century passed before the great importance of the theory was 
fully recognized. 

Wollaston's Equivalents The uncertainty connected with 

the atomic weights as determined by Dalton, led Wollas- 
ton, his countryman, to suggest the use of the term equiva- 
lent instead. This term he drew from the work of Richter ; 
and he meant by it the relative quantities, or proportions, in 
which bodies unite, thus doing away with the idea of atoms. 
Oxygen was taken as the standard, and given the value ten. 


He hoped, by the substitution of the idea of equivalent pro- 
portions, to escape all questions as to the number of the 
atoms in a compound. It is easy to see that his 'method 
rather increased than diminished the complications. 

Prout's Hypothesis. — In the year 1815 Prout published 
an hypothesis based on the assumption that all the atomic 
weights were whole numbers, and therefore multiples of 
hydrogen, and that these elements were consequently only 
different grades of condensation of hydrogen, which was 
therefore the primal element. No proofs whatever were 
offered in support of this bold theory. A little arithmetic 
only was needed to show its wildness, and the most approved 
work of chemists since has only shown the fallacy of the 
assumption on which it was based. Yet this hypothesis has 
proved itself exceedingly attractive to some of the master 
minds of chemistry, and has wrought much harm, as all false 
hypotheses must. Because of this very lack of foundation 
no overthrow could be complete. Although it has suffered 
many reversals, it still comes to life every now and then. 
Prout, the author of it, was a physician, and did little 
chemical work of value. 


It has been necessary to devote a good deal of time and 
space to the growth of theories in these, the first two decades 
of the new chemistry. These form the foundation of the 
modern science, and a correct understanding of them and 
their development is most important. It is well to turn now 
to the multiplication of chemical facts, especially to the 
growing list of chemical elements. 

Klaproth (1743-1817) Among the eminent discoverers of 

this period stands Klaproth. As has been said, it was largely 


through his influence that the German chemists were won 
over to the views of Lavoisier. His work was mainly in 
connection with the analysis of minerals and the improve- 
ment of analytical methods. He added uranium, titanium, 
and zirconia to the known bodies. 

Proust The work of Proust in connection with the 

study of tin, copper, iron, nickel, antimony, cobalt, silver, 
gold, and mercury, was most accurate and valuable for the 
extension of chemical knowledge. This was a part of the 
work brought out by the celebrated controversy over the Law 
of Definite Proportions already mentioned. But the two 
most distinguished discoverers in the first quarter of this 
century were Davy and Berzelius. Their influence upon the 
science has been very great. 

Sir Humphry Davy (1778-1829). — The scientific training 
of Sir Humphry Davy was secured while apprenticed to a 
surgeon and apothecary at Penzance. At the age of twenty 
he was put in charge of the laboratory of the Pneumatic Insti- 
tution at Bristol, founded by Dr. Beddoes for the application 
of gases to the treatment of diseases. Davy's surroundings 
here were most propitious for a successful career of scientific 
research. His laboratory was well furnished, and was sup- 
ported by the subscriptions of scientific men. He had plenty 
of time at his disposal, and the age was one of discovery and 
rapid progress in the science. His experiments related 
chiefly to nitrogen monoxide, or nitrous oxide ; and in a short 
time he published his " Researches Chemical and Philosophi- 
cal, chiefly concerning Nitrous Oxide and its Respiration." 
His courage and his determination were well proved by these 
experiments. The effects of this gas, supposed to be poison- 
ous, were tried upon himself. He discovered its anassthetic 
action. He exercised care, but was unflinching in his deter- 


ruination to get at the truth, and persevered, though often 
overpowered, weakened, and injured in health, by his tests 
imposed upon himself. While in this laboratory he gave 
some of his time also to experiments upon the decompositions 
caused by the aid of the electric current. 

Davy next became professor of chemistry at the Royal 
Institution in London, where all apparatus needed by him 
was freely supplied, and only occasional lectures were required 
of him. 

Decompositions by Means of Electricity. — He had for some 
time been thinking that the most needed step in chemistry 
was the decomposition of some of the bodies then regarded 
as simple or elementary, among them the alkalies and earths ; 
and having already, before moving to London, begun to apply 
the voltaic pile in chemical work, he thought this the most 
promising means for the solution of the question as to whether 
these bodies were really elementary or not. Nicholson and 
Carlisle had made the observation, in the year 1800, that 
water was decomposed into its components by the discharge 
from the voltaic pile. This led to similar experiments upon 
other substances, among them the remarkable ones of Berzelius 
and Hisinger upon salt solutions, ammonia, sulphuric acid, etc. 

Decomposition of Water. — Davy was among the first to 
busy himself with this most interesting and important ques- 
tion, the decomposition of water. From the very first it was 
noticed in this electrolysis that acid and alkaline substances 
were formed, and it was believed that water was changed 
into these under the action of electricity. By most careful 
experiments, Davy showed the error of this view. He car- 
ried out this electrolysis in vessels of various materials, and. 
showed that the products mentioned, the acid and alkali, were 
due to the glass, or to the matter dissolved in the water, or to 
the air itself. If the water, distilled in silver, was electro- 
lyzed in gold vessels, in an atmosphere of hydrogen, the acid 
and alkali did not appear. 


Davy further repeated and confirmed the work of Berze- 
lius upon salt solutions. He, too, made the observation which 
Berzelius had made, that the electric current separated hy- 
drogen, the metals, metallic oxides, alkalies, and earths to the 
negative pole, and oxygen and the acids to the positive. He 
concluded that the first named substances have a positive 
electrical energy, and the latter a negative ; and this was the 
beginning of the electro-chemical theory. Davy sought to 
explain all chemical combination and decomposition on this 
principle. According to him the heat noticed in certain cases 
of combination were manifestations of electricity. 

Davy was the first to bring the thought to a fixed form 
that electric and chemical action may be referred to the same 
force. All the later doctrines that chemical changes are 
merely the evidences of electrical attractions depend upon his 
work and views. 

Decomposition of the Alkalies. — In his first experiments 
upon potash and soda, Davy used strong solutions, and noticed 
that only hydrogen and oxygen were evolved. He next 
allowed the current to pass through melted potash. A flame 
appeared at the negative pole, and on changing the direction 
of the current " aeriform globules which inflamed in the air, 
rose through the potash." When the potash was placed upon 
a piece of platinum which was made the negative pole of a 
powerful battery, and the positive pole, in the form of a plati- 
num wire, brought in contact with the upper surface of the 
potash, the potash became hot, and even melted with the 
piassage of the current ; and on the lower (negative) platinum 
small globules, lustrous and metallic, much like quicksilver, 
were soon noticed, some bursting and burning, others tarnish- 
ing and coating over with a white film. 

Great was Davy's delight at his discovery ; and we can 
hardly exaggerate the impression made upon the chemical 
world by the decomposition of this supposed elementary body, 


and the wonderful new metal gotten from it. Its properties 
were most opposed to those which were held to be character- 
istic of the metals, light, oxidizing immediately in air, and 
decomposing water. 

Davy decomposed soda also. He named the new metals 
potassium and sodium, and confirmed his discovery by oxidiz- 
ing them back to the original alkalies. He learned how to 
prepare larger quantities and to preserve them under naphtha. 
These discoveries were made in 1807, and were followed next 
year by the decomposition of the alkaline earths, lime, baryta, 
and strontia. He also was convinced by his experiments that 
silica, alumina, zirconia, and beryllia could be decomposed by 
the electric current; but he failed to obtain any of the sup- 
posed elements existing in these substances. This he attrib- 
uted to his current not being powerful enough. Davy's 
discoveries confirmed the view, which was already widely held, 
that the alkalies and earths were metallic oxides ; that is, it 
confirmed this view in part, because it was not yet known that 
these were really hydroxides. 

Composition of Muriatic Acid, and the Nature of Acids. — His 
next important services were in connection with the theory of 
acids. Berthollet, in his work upon hydrogen sulphide, 
hydrochloric acid, and hydrocyanic acid, had really shown the 
untenable character of Lavoisier's theory as to oxygen being 
present in all acids, and hence deserving of its name, the acid- 
maker. But Berthollet' s experiments were not pressed to 
their legitimate conclusion ; and . the theory of Lavoisier still 
held its place, though the existence of hydrochloric acid 
became a serious stumbling-block. Oxygen, according to 
Lavoisier's theory, should have been one of its constituents, 
and yet no one could detect it. If this acid contained oxygen 
its salts should also. In 1774 Scheele had shown that by its 
action upon the black oxide of manganese, a yellow, pungent 
smelling gas was obtained. Berthollet showed that a solution 


of this gas in water gave off oxygen when exposed to sunlight, 
and hydrochloric acid was at the same time formed. There- 
fore it was called "oxidized muriatic acid." Muriatic acid 
was regarded as composed of oxygen and an unknown radical. 
These were not the views of Scheele, who called chlorine 
" dephlogisticated muriatic acid," and regarded it as hydro- 
chloric acid deprived of its phlogiston or hydrogen. In 1809 
Gay Lussac and Thenard showed that one volume of " oxi- 
dized muriatic acid " and one volume of hydrogen united to 
form muriatic acid. This proved that it contained hydrogen. 

Davy next endeavored to find the oxygen which was sup- 
posed to be in this acid, but without success. He did show, 
however, that when " oxidized muriatic acid " acted upon metals, 
salt-like compounds were gotten, and that similar compounds, 
and at the same time water, were formed by the action of 
muriatic acid upon metallic oxides. Davy explained these 
facts by regarding " oxidized muriatic acid " as an elementary 
substance, and muriatic acid as its compound with hydrogen ; 
but chemists were slow to accept his views. Davy held that 
this element, to which he gave the name chlorine, resembled 
oxygen in many respects, and, in a limited sense, was also to 
be regarded as an acidifier and supporter of combustion. In 
the ensuing discussion with Gay Lussac, who endeavored to 
prove from the work of Berzelius and Davy on ammonium 
amalgam, and from the action of potassium on ammonia, that 
hydrogen was an alkalizing principle, Davy uttered the fol- 
lowing important but often overlooked truth : — 

'• The substitution of analogy for fact is the bane of chem- 
ical philosophy; the legitimate use of analogy is to connect 
facts together, and to guide to new experiments." 

Davy's facts were clear and convincing, and in a few years 
chlorine was generally regarded as an element. In 1812 and 
1813 iodine, discovered by Courtois, a French soapmaker, and 
investigated by Gay Lussac, was added to the list of acidifiers. 


The New Theory of Acids. — These new facts necessitated a 
new theory of acids. No one element could be regarded any 
longer as the acid-making principle. Most, if not all, con- 
tained hydrogen ; but the acid properties seemed to be depend- 
ent upon the other element or elements combined with the 
hydrogen. An acid might contain oxygen and be an oxy-acid, 
or contain no oxygen ; and so, too, a salt might contain oxygen, 
or, like the chlorides or iodides, have none in its composition. 
Thus the old view, that a salt was a compound of the oxide of 
a non-metallic element, or acid, and of the oxide of a metal, 
or base, was overthrown, and salts came to be looked upon 
as metallic derivatives of acids, the metal replacing the 

The Alkalizing Principle. — In this connection it is well to 
take up the discussion which arose as to the constitution of 
the alkali metals, sodium and potassium. Davy had observed 
that these metals separated at the negative pole, while oxygen 
appeared at the positive ; also that they had the power of 
reducing metallic oxides ; and showed that by their combus- 
tion in oxygen the alkalies seemed to be regenerated. Hence 
he concluded that these bodies were metallic and elementary. 
From his work upon ammonium amalgam, a little later, he 
concluded that this was composed of mercury and a hypo- 
thetical metal-like body, ammonium, which broke up into 
hydrogen and ammonia. The relationship between this body 
and the alkalies, and the analogy between their amalgams, 
gave rise to the theory that these also were combined with 
hydrogen, a theory which Davy was more inclined to accept 
because of the combustibility of these metals. Gay Lussac 
and Thenard had examined also the action of potassium upon 
ammonia gas, and noted the liberation of hydrogen and the 
formation of a green substance, the amount of hydrogen 
liberated being the same as that set free by potassium from 
water. From the green substance they regenerated the origi- 


nal amount of ammonia used. Therefore they said that 
potassium consisted of potash and hydrogen, and that this 
hydrogen was set free by treatment with water or with 
ammonia. According to this theory, there was an alkalizing 

Davy soon returned to his original ideas as to these alkali 
metals, and gave as his explanation of the experiments of Gay 
Lussac and Thenard that the hydrogen came from the decom- 
position of the ammonia, and not from the potassium. In the 
year 1811, Gay Lussac and Thenard came over to Davy's 
views, having observed that the body gotten by the burning 
of potassium was not the same as potash, but contained less 
oxygen, and that the melted potash was not water-free, as 
Davy had imagined. Thus they gave up their theory that 
hydrogen was an alkalizing principle, giving bases when com- 
bined with ammonia, or soda, or potash, and similar bodies. 
The theory of acids, salts, and bases has become of much less 
interest and importance in the progress of chemistry than it 
was in the earlier period of the history. 

Davy's Later Life. — For his services in inventing the 
safety-lamp, Davy was made a baronet. In 1820 he was 
elected President of the Royal Society of England ; and he 
held this post for seven years, the highest position attainable 
by an English man of science. He died in 1829, one of the 
most brilliant chemists the world has ever seen, and the 
greatest England has produced. 


It was peculiarly fortunate for chemistry that two such 
brilliant and accurate investigators as Davy and Berzelius 
should have appeared at a time when the framework erected 
by Lavoisier needed filling out, and the foundations of the 
science had to be deepened and broadened. A series of 


mediocre and inaccurate workmen coming just then would 
have more easily misled and more seriously retarded the 
science than at any later period. Berzelius was a greater 
chemist than Davy, and the chemist of to-day can scarcely 
overestimate his indebtedness to him. 

Berzelius (1770-1848) Johann Jacob Berzelius was born 

in Sweden, one year after the birth of Davy. Poverty greatly 
hampered both in their younger years, and both were forced 
to follow medicine and pharmacy as a means of livelihood at 
first. Berzelius became a professor of chemistry in Stock- 
holm. Here he lacked the appliances and the leisure 
afforded Davy by the freedom .from class-work at the Boyal 
Institution. Still, his lectures and classes enabled Berzelius 
to impress himself and his views upon the rising generation 
of chemists. This end Davy could only partially attain 
through his published papers and books. 

Among the most distinguished of his pupils may be men- 
tioned Mitscherlich, Magnus, Mosander, Heinrich and Gustave 
Bose, Gmelin, and Wohler. His career was further compar- 
able to that of Davy in that he held an honored post, namely, 
that of permanent secretary to the scientific society of his 
native land, and was ennobled by his king. His later years 
were devoted to literary labors ; and he died in 1848, nearly 
twenty years after the death of Davy. 

The Work of Berzelius. — It is difficult to give a short and 
at the same time fair account of the work of this great man, 
as it covered almost the entire field of chemistry, and hence 
was of the most extensive and varied character. Only brief 
reference can be made to special chemical work. More stress 
will be laid upon his services in the direction of the develop- 
ment of chemical theory. Berzelius was a most accurate and 
painstaking worker, showing great powers of observation and 
a close attention to details. He was conservative, holding 


fast his allegiance to older views until he saw clearly that the 
new were substantiated by the facts. For instance, the imper- 
fection of Dalton's atomic theory, and his arbitrary rules for 
determining the number of atoms in a compound, at first 
made him hesitate to accept it. When he did accept it, how- 
ever, he endeavored to extend its application into every branch 
of chemistry. 

Analytical and Experimental Work. — He brought about 
many improvements in analytical chemistry, devising many 
methods for the separation and determination of the elements. 
His close attention to details led him to the discovery of 
selenium, ceria, thoria, and many new compounds. He also 
first prepared the elements silicon, zirconium, and a purer 
tantalum, and did much towards enlarging the knowledge of 
the platinum metals. He made a great number of analyses to 
prove the constancy of proportions, and the truth of Dalton's 
law of multiples. He enriched mineralogy by a great number 
of analyses of minerals, and showed that minerals were simply 
chemical compounds obeying the atomic laws. Based upon 
this he introduced a chemical system of classification for 
them. He extended the law of multiple proportions to 
organic chemistry, and did much to systematize that branch 
of the science. 

Determination of Atomic Weights. — Berzelius and the 
pupils in his laboratory undertook the determination of the 
atomic weights. The analytical work, of course, greatly 
excelled that of Dalton, and in the rules laid down for his 
guidance in deciding the number of atoms in a given com- 
pound or molecule, he showed a greater knowledge ; still, his 
rules were, in some respects, arbitrary and unsatisfactory. 
His standard was oxygen taken as 100. Many of his deter- 
minations are still quoted, and made use of in settling these 
physical constants, over which chemists have been so long 
busied. This work was begun at a time when Wollaston was 


endeavoring, by his use of the term equivalents, to do away 
with the whole vexed question of atoms. Thomson, adhering 
to Dalton's theory, was using the standard oxygen equal to 
one, believing that this would give more of the atomic weights 
as whole numbers. 

Berzelius, in 1813, made a great step forward in recogniz- 
ing the distinction made by Avogadro between atoms and 
molecules, and in accepting the law of Gay Lussac that equal 
volumes of gases contain equal numbers of atoms. He limited 
its application, however, to elementary gases. The weights of 
the combining volumes of these gases were, he believed, the 
weights of their respective atoms. Still, Berzelius's use of 
Gay Lussac's law was too limited to free him from the neces- 
sity of adopting rules for deciding the number of atoms in 
compounds. He gave a fairly complete table of these weights 
in 1818. 

The Introduction of Symbols. — Berzelius also greatly aided 
the progress of chemistry by the introduction of symbols. 
He proposed that the first letter of the Latin name of the 
element should be used to designate the element, and should 
represent one atom or one equivalent of it. A compound is 
thus represented by placing the proper number of these 
symbols side by side. Thus, H is hydrogen, CI is chlorine, 
and HC1 is hydrogen chloride. He supposed the existence of 
certain double atoms (where two atoms of an element occur 
together). These were indicated by a mark across the symbol ; 
thus HO was water, or, as we write it, H 2 0. For convenience' 
sake, an atom of oxygen was often indicated by a point or 
dot, an atom of sulphur by a mark at right angles, thus : — 

Carbon Dioxide, C; "Nitrous Acid," N; Potassium Nitrate, KN. 

These symbols were a great advance over those suggested 
by Dalton, which were diagrammatic and quite unpractical, 
For instance, the following are some of Dalton's symbols : — 


Hydrogen, Nitrogen, (I) Carbon, • 

Oxygen, O Water, GO Carbonic Acid, 0«0 

ItnricAcid, m Potash, (111) Soda, Oil/ Barium Chloride, AoA 
O O ° OO U 8 U 

The symbols introduced by the ancient alchemists, and 
partly used by them in later times, carried with them the idea 
of the connection between the metals and the heavenly bodies, 
and were intended, apparently, to mystify rather than to 
simplify the science. Mention has already been made of 
their great number and diversity. 

The Dualistic Theory. — The term atom was extended 
farther by Berzelius, to include what he looked upon as com- 
pound atoms. These were built up of two parts, each of 
which might be a simple atom or several atoms, in which each 
of the two parts acted as a single, simple atom. This was 
the dual structure, and forms the dualistic system of Berzelius. 
It dominated all of his ideas and theories with regard to 
chemical phenomena, and for more than a decade held a pre- 
eminent position in chemistry. Berzelius seemed to have 
formed this idea of dualism from his observations upon the 
volumes of gases. For a certain number of these gases the 
equivalent is formed of two atoms. This was true not only of 
hydrogen, but of nitrogen, chlorine, and others, in the form of 
vapor. The atomic weights of these bodies represent also the 
specific gravities, or the weights of one volume compared with 
one volume of the standard ; but since it needs two volumes 
of nitrogen, two volumes of chlorine, etc., to form the first 
stage of oxidation with oxygen, two volumes of nitrogen, etc., 
represent the equivalents of these bodies compared with 
oxygen. He considered that these atoms, then, were united 
two and two, and called them the double or compound 

The Electro-Chemical Theory. — Before any full discussion 


of the dualistic theory, it is necessary to study the electro- 
chemical theory, which we owe partly to Davy, though chiefly 
to Berzelius. These two theories are so closely linked together 
that one is unintelligible without the other, at least as they were 
held by Berzelius. As to the author of this theory, it was mainly 
developed by Berzelius. That which was more a philosophi- 
cal conception on the part of Davy, a vision of the two forces, 
electrical and chemical, existing side by side everywhere in 
nature, and holding all things in equilibrium, was reduced to 
precision and made the basis of a system of chemical classifi- 
cation by Berzelius. This theory was offered as, in a measure, 
explaining the nature of chemical affinity. The term affinity, 
as meaning the chemical attraction of a particle of one kind of 
matter for another, had been in use a long while. The differ- 
ences in this force had been noticed ; and, as we have seen, 
elaborate tables of affinity had been constructed by many 
chemists. Berthollet had caused a great depreciation in the 
value of these tables by showing how cohesion, mass, and tem- 
perature influenced the exhibition of affinity. Berzelius 
emphasized what had already been noted, that this force is 
exhibited between unlike atoms, and differs greatly in inten- 
sity between different atoms, some showing almost no affinity 
for one another, and others very great. According to Berze- 
lius, this exhibition of affinity depended upon the electrical 
states of the different atoms. This view, of course, is based 
upon the two facts that compounds are decomposed by the 
electric current, and the constituents invariably seek the same 
respective poles ; and, secondly, that chemical union can be 
caused by the action of electricity. 

The Berzelian theory was, that every atom had a certain 
quantity of electricity belonging to it, partly positive and 
partly negative. This, accumulated at the extremities of the 
atoms, gave a positive and a negative pole. Because of the 
preponderance of one or the other of these kinds of electri- 


city, however, the whole atom has the character of either a 
positively or a negatively electrified body. There is a neu- 
tralization of the positive electricity by the negative on the 
combination of the atoms. Obeying the ordinary rule, atoms 
similarly electrified would show little or no affinity for one 
another, whereas great affinity would be shown between those 
of very different electricities. 

Although, in a compound atom, the union was brought about 
by a neutralization of the different electricities, still, in the 
Berzelian theory, the atom, as a whole, was characterized by 
either positive or negative electricity, according to which pre- 
dominated, and exerted its attractive or repellent influence on 
the other atoms. Every compound atom, then, was built up of 
two parts, one positively and the other negatively electrified, 
and formed a dual structure. The system, hence, was known 
as the dualistic. 

Thus a base became regarded as an electro-positive oxide, 
and an acid as electro-negative oxide ; and Lavoisier's theory 
as to the acid-making oxygen could not possibly be used any 
longer. The electro-chemical theory dominated chemistry dur- 
ing the third and fourth decades of this century. It went too 
far in advance of observed and proved facts. It is strange 
that the conservatism of Berzelius should have permitted him 
to assume so much, and go so far beyond that which he could 
prove. In particular, his identification of chemical affinity 
with electrical polarity was one not justified by the facts. The 
beauty of the theory as one explaining, and that most plausi- 
bly, the mysterious chemical force or affinity which had puz- 
zled chemists for so long a time, probably proved the attraction 
which overcame the scruples of Berzelius. The work of Ber- 
zelius in connection with organic chemistry will be spoken of 
later on. 



Summing up now the status of the science, as was done at 
the beginning of this period, we find chemistry in the posses- 
sion of a rational and systematic nomenclature ; a solid founda- 
tion in the laws of constant proportions and multiples, and 
a satisfactory working hypothesis and theory explaining them 
in the atomic theory of Dalton ; a simple and practical system 
of symbols ; and, lastly, a remarkably accurate table of those 
most important physical constants, the atomic weights, the 
determinations of Berzelius being a near approach to the more 
accurate work of the present day, as can be seen by the fol- 
lowing table, in which the numbers of Berzelius have been 
calculated on a basis of hydrogen as unity, instead of oxygen 
equal to 100, as adopted by him : — 


















The science was thus well furnished for entering upon the 
era of marvellous growth in the accumulation of facts and in 
the formation of theory which the seventy-five years since 
passed have seen. 

New Appliances. — Improvements in the methods of re- 
search and in appliances were the great needs of the times. 
Volta and Galvani had brought electricity into a form to be 
useful to chemists ; and so remarkable had been the results, 
that it is not surprising that too much should have been ex- 
pected of it, and many phenomena, imperfectly understood, 
attributed to this energy, itself so mysterious. 


There had been marked improvement in laboratory appli- 
ances. Glass, porcelain, and platinum were the materials of 
which the apparatus was made, and the forms were being 
constantly improved. Gold and silver were also used for 
some of the vessels. Yet one accustomed to the elegant fur- 
nishings of a modern laboratory would look with surprise 
upon the simplicity and even poverty of the rooms in which 
some of the great masters worked. 

Berzelius's Laboratory Wohler has described his first 

visit to the laboratory of Berzelius, in which so many famous 
discoveries had been made. 

" No water, no gas, no hoods, no oven, were to be seen ; a 
couple of plain tables, a blow-pipe, a few shelves with bottles, 
a little simple apparatus, and a large water-barrel whereat 
Anna, the ancient cook of the establishment, washed the 
laboratory dishes, completed the furnishings of this room, 
famous throughout Europe for the work which had been done 
in it. In the kitchen which adjoined, and where Anna 
cooked, was a small furnace and a sand-bath for heating 

Apparatus. — It has required the combined ingenuity of 
chemists and of workers in glass, pottery, and metals for 
many years to produce the almost countless forms of delicate, 
costly, and often complicated apparatus of the present day; 
but the demand for greater accuracy and increased precision 
has made such inventions necessary. At the time of Davy 
and Berzelius, the chemist was expected to be something of a 
mechanic, able to cut and form, fashion and solder, the 
wood, brass, and iron into the various shapes he needed. He 
must also have skill as a glass-blower, for in most cases he 
would have to depend upon his own cunningness of hand 
for the success of his experiments. It would be well in, 


these days, also, for chemists to have at least some of this 
mechanical training ; but few have the time for it, or give the 
time to it, since far more skilful hands are ready to do their 

Law of Dulong and Petit. — But new methods are even 
more valuable than improved forms of apparatus. It is im- 
possible to give even in outline the improvements in analytical 
methods, in reagents, tests, modes of separation, etc. " The 
larger field of methods based upon natural laws can, how- 
ever, be touched upon. In the matter of atomic weight 
determinations, two methods were devised for securing greater 
accuracy and certainty. Both of these important physico- 
chemical discoveries were made in the year 1819. 

Dulong and Petit, in experimenting upon the specific heats 
of the metals and other bodies, came upon the important 
truth that these were very nearly inversely proportional to 
their atomic weights. Multiplied by their atomic weights, the 
specific heats gave a constant quantity. This gave the law 
as stated by them : the atoms of the different elements have 
the same capacity for heat. It is easy to see that by means 
of the specific heat one could readily approximate to the true 
atomic weight, and arrive at a decision as to which of two or 
more possible figures represented the true weight. 

There were exceptions to the law which have been ex- 
plained away only in late years. Still, the law was extended 
to simple chemical compounds, and proved of great use after 
it was more fully understood. Berzelius opposed the accept- 
ance of it at first, in part, because it would necessitate a 
revision of his table of atomic weights, and might endanger 
the accepted views as to some of the atomic relations. He 
gradually gave up this stand, however, when the law was 
confirmed by other workers, and more accurate determinations 
were made than the first ones of Dulong and Petit. 


Law of Mitscherlich Another aid in this direction was 

the Law of Isomorphism, discovered by Mitscherlich. While 
engaged in a research upon the salts of phosphoric acid and 
arsenic acid, he conceived the law that compounds of analo- 
gous composition and containing the same number of atoms 
crystallize in the same crystalline form, or, in other words, are 
isomorphous. For this to be really useful in determining 
atomic weights, it was necessary to reverse it, and to have it 
hold true that isomorphous bodies were analogous and con- 
tained the same number of atoms. Here many difficulties 
presented themselves, necessitating narrower and narrower 
definitions of isomorphism. It is evident that, though anal- 
ogy or similarity of crystal form may have a bearing upon 
the molecular composition and arrangement, we are unable as 
yet to determine fully this bearing. Berzelius took up the 
discovery of Mitscherlich as one of the most important of 
that age, and made frequent use of it in testing his atomic 

Corrected List of Atomic Weights Seven years later, or in 

1826, he published a corrected table of the atomic weights, 
in which he made use of all of these discoveries and improve- 
ments. In this table, for the first time, the atomic weights 
of nitrogen and chlorine as elements are given. 

Electro-chemical Equivalents Mention should be made in 

this connection also of Faraday's noteworthy observation that 
the same electric current, in decomposing different electro- 
lytes, such as water, metallic chlorides, etc., separated at the 
negative or the positive pole equivalent amounts of the re- 
spective constituents. This was called the law of constant 
or fixed electrolytic action, and the amounts separated were 
the electro-chemical equivalents. Faraday thought that the 
determination of these equivalents would prove a valuable 


aid to the correct determination of the atomic weights. Bsr- 
zelius, however, denied the usefulness of numbers derived in 
the electrolytic way. 

Work of Dumas on the Atomic Weights. — In their work 
upon the atomic weights, Dumas and the French chemists 
made especial use of the law of volumes as given by Gay 
Lussac, and adopted the distinction made by Avogadro be- 
tween the atoms and molecules. The equivalents suggested 
by Wollaston were rejected by them as applicable only to a 
limited range of substances, such as acids and bases, besides 
being indefinite or indeterminable when indentified with com- 
bining weights, as many bodies united in several different 
proportions to form compounds. Thus copper in one oxide 
bears the ratio of eight to one to the oxygen, in another the 
ratio of eight to two. Taking oxygen as unity, the equivalent 
of copper could be reckoned as either eight or four. Some of 
Dumas' determinations, as those of phosphorus, tin, and sili- 
con, show that he did not realize the full importance of 
Avogadro's theory as an aid in such determinations. Still, he 
believed that this theory gave a surer basis for solving such 
questions as this about the copper ; and he constructed a table 
of atomic weights, making use of this theory and the law of 
Dulong and Petit. Of course he made use of the writings 
of his countryman, Ampere, mentioning Avogadro only once. 
He made use of the term elementary molecules, and said that 
there was no means of deciding of how many smallest parti- 
cles these molecules consisted. In accuracy and correctness 
these weights fell below those of Berzelius. 

Vapor Densities To confirm his ideas, he extended his in- 
vestigations of the truth of Avogadro's law, devising, in 1827, 
apparatus and a most excellent method for the determination 
of the specific gravities of gases at high temperatures, thus 


enabling him to experiment upon the vapor densities of iodine, 
phosphorus, sulphur, mercury, etc. His results, instead of 
confirming, tended rather to disprove the law of volumes. 
We know that the trouble lay in the complex nature of the 
molecules experimented upon, but of course this was unknown 
to Dumas. He finally declared that, even in case of the 
simple gases, like volumes did not contain equal numbers of 
chemical atoms. Berzelius also had been forced practically 
to give up the law of volumes, at least so far as any use in 
atomic weight determinations was concerned, limiting its 
application to the uncondensed or so-called permanent gases. 
Dumas' work would induce one to give it up even for these. 

Unsatisfactory Condition of Chemical Theory Chemists, 

therefore, looked with indifference or disfavor on this law, 
which is the mainstay of modern work upon the atomic 
weights. The law of Dulong and Petit was shown also to 
have some notable and unexplained exceptions, and Mitscher- 
lich, by his further discovery of dimorphism, had thrown 
much doubt upon his law of isomorphism. So, at the close 
of the thirtieth year of this century, the atomic theory was 
regarded by many chemists as either disproved or relegated 
to a very hypothetical position. 

Gmelin's Views Some took up again the equivalents of 

Wollaston. Certainly, little distinction was made between 
these and the atoms of Dalton, and the dualistic system of 
Berzelius lost ground. Leopold Gmelin, the author of the 
most complete handbook or encyclopaedia of chemistry up to 
his time, and the most influential, going through many 
editions and forming the basis subsequently of Watt's "Dic- 
tionary of Chemistry," was the leader in this new school of 
chemists. In the edition of his handbook published at this 
time, the fourth decade, he gave up the atomic theory com- 


pletely. He recognized no difference between chemical com- 
pounds and mixtures. Two substances, according to Ms 
ideas, could combine in an unending number of proportions. 
This was especially true where the affinity between them was 
weak. In the case of a strong affinity the tendency was to- 
ward a limitation to a few proportions. To each body, then, 
a sort of mixing weight could be assigned, and this number 
could be used in stoichiometrical calculations. 

His table of the equivalents halved most of the atomic 
weights. Thus H = 1, = S, S = 16, C = 6, etc. Water be- 
came HO. The rule was to make everything conform to the 
utmost simplicity. Where there was a choice between several 
possible equivalents for any one element, he took the least and 
simplest. These numbers and formulas were retained by 
many chemists for decades afterwards, and by some, in part, 
for as long as a half .century. 

Need of New Support for the Atomic Theory This long 

struggle over the atomic theory, and very unsatisfactory end- 
ing of it, led many to look upon theorizing as something to 
be avoided, and to regard as the true object of chemistry the 
search after facts. To such minds there was no place for the 
imagination in science. To rescue the theories of chemistry 
from this disrepute it was necessary to call in the aid of the 
growing science of organic chemistry ; and it is through this 
branch of chemistry that the doubts and difficulties were 
mainly cleared away and chemical theory advanced. 




In the text-book of Lemery, in use in the latter half of the 
seventeenth century, all chemical substances were classified 
and separately treated under the three headings, mineral, vege- 
table, and animal substances. This division was made first 
at this time, and was the usual one during the next century. 
This corresponded with the favorite grouping of the " three 
natural kingdoms " which were so much used in books of 
two or three generations ago. 

Lavoisier's Views Lavoisier showed that organic sub- 
stances were composed mainly of carbon, hydrogen, and oxy- 
gen, together with nitrogen, and, less frequently, phosphorus 
and sulphur. Before this there were great doubt and discus- 
sion as to their composition. Lavoisier was the first to devise 
a system of quantitative analysis for these bodies, and so to 
decide definitely as to their composition. Acid bodies were 
recognized among organic substances ; and so, in his acid 
theory, Lavoisier accounted for their nature by supposing 
that in these cases the oxygen was combined with a com- 
pound radical or organic residue. This idea of the compound 
radicals was afterwards developed by Berzelius and his fol- 
lowers until organic chemistry became the chemistry of the 
compound radicals. 

-^ 115 


Organic Substances as the Products of Life Force First the 

barrier between vegetable and animal substances fell away 
when it became clear, from the work of Chevreul, that many 
of the fats and acids and other substances, occurring in both 
kingdoms, were identical ; but the line was still very sharply 
drawn between mineral substances and the products of plant 
and animal life. These latter, it was believed, could not be 
artificially formed out of the elements that composed them. 
They were produced by some mysterious force, life, whose 
operations could not be imitated. The ordinary laws govern- 
ing chemical affinity could not be expected to apply in this 
field ; and hence chemical theories, as the atomic theory, could 
not explain the phenomena of life. This complete separation 
may have been a natural reaction from the attempt of the 
earlier chemists to explain all life processes by means of 
faulty chemical theories. 

Views of Berzelius Berzelius was the first (1811) to at- 
tempt to prove that organic substances were nothing more 
than ordinary chemical compounds, obeying the laws of con- 
stant and multiple proportions, and offering a fair field for the 
application of the atomic and other theories. With improved 
appliances and analytical methods he succeeded in showing 
the correctness of his views, but only after years of labor. 

The Theory of Compound Radicals In the third decade, 

Berzelius looked upon these substances as composed in the 
same way as the inorganic compounds, only having compound 
radicals in the place of elements. To the compound radicals 
he attempted to apply his dualistic theory. To his ideas as to 
these radicals he was especially led by the research of Gay 
Lussac upon cyanogen, in which he showed that this radical 
played the role of an element. Attempts were multiplied to 
discover the various organic substances having complex group- 


ings of atoms which functioned as elements. Thus, Gay Lussac 
looked upon alcohol as ethylen and water. Dobereiner re- 
garded oxalic acid as carbonic acid and carbon monoxide. As 
Berzelius pointed out, this was opposed to the electro-chemical 
theory, and there was danger of confusion and error. 

Isomerism The search for the proximate constituents in 

organic substances brought about a rapid development of the 
science, leading especially to many efforts at settling the 
chemical constitution of these bodies. One of the most im- 
portant of the discoveries in the third decade was that of 
isomerism. This was looked upon as an error by chemists at 
first, so little prepared were they to believe that bodies simi- 
larly composed could be chemically and physically different. 
It was in the year 1823 that Liebig announced that his analy- 
sis of silver fulminate yielded the same results as Wohler had 
found in the preceding year for his silver cyanate. He was 
confident that his figures were correct, and believed that 
Wohler must have made a mistake. A careful repetition of 
the analyses showed him that both were correct ; and so it was 
proved that two bodies, totally unlike, could and did have the 
same composition. Gay Lussac saw that the only explanation 
of this lay in the different mode in which the elements were 
united with one another. Berzelius hesitated to accept the 
facts or any generalization from them. Then followed in 
1825 Faraday's discovery of an isomer of ethylen chloride, 
and in 1827 Wohler's transformation of ammonium cyanate 
into urea. Berzelius himself showed the isomerism existing 
between tartaric and racemic acids ; and the chemical world 
became accustomed to the new fact of isomerism, for the ex- 
planation of which the atomic theory is so necessary. Berze- 
lius suggested the name isomerism. He also adopted, as 
the most plausible explanation of isomerism, the different 
arrangement of the atoms ; and he seems to have thought it a 


possibility to determine the mutual relations of the atoms in 
their compounds, or the manner in which the atoms were 
united to the compound radicals or proximate constituents. 

The Synthesis of Urea One obstacle to the rapid growth 

of organic chemistry lay in the belief that while mineral sub- 
stances could be artificially produced, or synthesized, the 'imi- 
tation of organic bodies was beyond the reach of experimental 
methods, as they were the products of life itself, and could be 
formed only in the plant or animal cell. It is true that new 
organic preparations had been made by distilling and other- 
wise treating various products of plant life, but the original 
source or starting-point remained the same life products. 
Chevreul had shown that the natural fats were compounds of 
certain acids and the glycerine discovered by Scheele. Still, 
all of this did not do away with the belief in the necessity 
for the action of the mysterious life force. 

It was Wohler's brilliant synthesis of urea which finally 
broke down this barrier, proving the forerunner of many 
syntheses, and inciting numbers of workers to labor in this 
lucrative field. It is true that the synthesis had not been 
made directly out of the elements ; but still it was out of sub- 
stances then regarded as inorganic that he had prepared one 
of the most interesting and best known of animal products. 
Of course the dying away of the old belief was slow, but 
Wohler's discovery is commonly pointed to as marking the 
beginning of organic chemistry as a science. 

Organic Analysis Another obstacle to the rapid develop- 
ment of this branch of chemistry lay in the imperfection of 
the analytical methods. Lavoisier had laid the foundations 
for the correct analysis of organic bodies, and Gay Lussac, 
Eerzelius, and Dobereiner had successively improved upon 
them; but the operations were still slow, difficult, and not 


very accurate. In 1830 Liebig greatly perfected the methods 
of analysis, and his processes have not needed very many nor 
great modifications to fit them to the needs of the present 
times. Liebig's charcoal combustion furnace, his bulbs, and 
tubes are still sometimes used. 

Classification of Organic Substances A true and helpful 

classification of these bodies, now multiplying so rapidly, was 
lacking. In 1811 Gay Lussac and Thenard, interpreting the 
results of their analyses, had divided these bodies into three 
classes : — 

1. Those which contain just so much oxygen as is neces- 
sary to form water with the hydrogen present. These are 

2. Those containing less than that proportion of oxygen. 
These are resins and oils. 

3. Those containing more oxygen. These are the acids. 
Of course so primitive and faulty a classification as this 

was of little service. It merely serves to show that in the 
unsettled state of the ideas concerning these bodies no proper 
classification was possible. 

Extension of the Electro-chemical Theory In 1819 Ber- 

zelius declared that his electro-chemical theory could not be 
extended into organic chemistry, as here the elements were 
under the influence of life force. In decay, fermentation, etc., 
he saw evidences of a striving on the part of these elements 
to return to their normal condition. Later he extended both 
this theory and that of dualism into this branch of chemistry, 
seeing in the compound radicals the same dualistic condition 
which he thought existed in the compound atoms of the 
inorganic bodies. 

Further Extension of the Radical Theory There was con- 
tinued effort at extending the radical theory to organic 


chemistry. Thus, in 1828, Dumas announced that ethylen 
was such a radical, and gave a table of its compounds, 
endeavoring to show their analogy to ammonia and its com- 
pounds : — 

defiant gas or Ethylen, 2 C, H 2 . NH 3 , Ammonia. 

Hydrochloric acid ether, 2 C 2 H 2 NH 3 + H CI, Sal Ammoniac. 

+ HC1. 

Ether, 4 C 2 H 2 + H 2 O. 2 NH 3 + 2 H 2 0, Ammonium ox- 
Alcohol, 4C 2 H 2 , 2H 2 0. 

Acetic Ether, 4 C 2 H 2 , C 8 H 6 3 , 2 NH 3 , C 8 H 6 3 , H 2 O, Ammo- 

H 2 O. nium Acetate. 

Oxalic Ether, 4 C 2 H 2 , C 4 3 , 2 NH 3 , C 4 3 , H 2 O, Ammonium 

H 2 O. Oxalate. 

This was the so-called Aetherin theory, and was largely 
based on the ease with which alcohol could be converted into 
ether and ethylen. Thus the supposed Aetherin (C 4 H 4 ) was 
a base, forming hydrates with water, and salt-like ethers with 
acids. This must serve as an illustration of the imperfect 
attempts at discovering these radicals, and the great difficul- 
ties attending such researches. 

The Radical of Benzoic Acid The radical theory received 

its greatest support from the classical research of Liebig and 
W older (in 1832), " On the Radical of Benzoic Acid." This 
was hailed by Berzelius as heralding the dawn of a new day. 
It was certainly an epoch-making research, standing out as 
a masterpiece amid a mass of erroneous and imperfect re- 

These two great chemists, then young men, showed that 
in the oil of bitter almonds (benzaldehyde) and its many 
derivatives one group of atoms remained unchanged, and 
characterized the whole. This they called benzoyl. This 
brilliant work contributed much to the advancement of or- 


ganic chemistry by the valuable new methods of research 
which it introduced into the practice of the chemist. 

Changes in the Radical Theory Furthermore, a new prin- 
ciple was recognized. Hitherto it had been thought necessary 
to isolate the radical, and it was upon this rock that many of 
the efforts at finding these radicals had suffered shipwreck. 
Now, although benzoyl had not been isolated, one could as little 
afford to doubt its existence as that of magnesium or titanium 
(these being metals whose compounds were known a long 
time before the metals themselves were isolated) ; and thus 
chemists were aroused to a search for the common radicals in 
bodies which showed by their chemical behavior or modes of 
preparation that they belonged together. 

Berzelius and Liebig joined in this work with great suc- 
cess. The difficulty in recognizing benzoyl as a radical 
because of its containing oxygen was done away with by 
regarding it as the oxide of the radical proper. For the 
earliest idea of a radical was that it was a compound of car- 
bon and hydrogen only, and contained no oxygen. Thus, 
ether was the oxide of the radical ethyl ; but Berzelius en- 
tirely missed the connection with alcohol by regarding that as 
the oxide of the radical C 2 H„ . This was corrected by Liebig, 
who, however, doubled the formula of the radical ethyl, C 2 H 5 . 
Thus for him alcohol was the hydrate of ethyl, C 4 H 10 O, H.,0. 
Chemists agreed as to the existence of compound radicals in 
these various compounds. It is not surprising that they 
should differ as to the nature of the radicals themselves, when 
we consider that this was really only the beginning of organic 
chemistry, and the knowledge of these substances was very 
imperfect. Berzelius was inclined to the belief that these 
radicals were unchangeable. Liebig took a wider view of 
them, looking upon his grouping of the elements merely as a 
means to a better understanding of the transformations these 
bodies undergo. 


Chemistry of the Compound Radicals About 1837 this 

theory of the compound radicals reached its highest point of 
credit and influence. Liebig and Dumas united in valuable 
investigations, and this branch of chemistry was named after 
the dominating theory. 

How far this comparison went may be gathered from a 
quotation from a joint work of Liebig and Dumas : — 

" Organic chemistry possesses its own elements, playing at 
one time the role of chlorine or oxygen, at another that of a 
metal. Cyan, benzol, amide, the radicals of ammonia, of the 
fats, of alcohol, form the true elements of the organic nature ; 
whilst the simplest constituents, as carbon, hydrogen, oxygen, 
and nitrogen, become recognizable only when the organic 
material is destroyed." 

Liebig, in 1838, clearly defined a compound radical, giving 
three essential characteristics, and using cyanogen as a type. 

1. We call cyan a radical because it is an unchanging con- 
stituent in a series of bodies or compounds. 

2. Because it can be substituted in these by other simple 

3. Because, in its compounds with a simple body, this last 
can be separated and substituted by another simple body. 

At least two of these conditions must be fulfilled for a 
group of atoms to be regarded as a radical. 

This radical theory unquestionably aroused great interest, 
and stimulated chemists to much fruitful and even brilliant 
work. Thus, one may mention the research of Bunsen upon 
the kakodyl compounds, which formed, indeed, one of the 
strongest supports of the theory. 

The Atomic Theory Confirmed The dualistic theory and 

the theory of compound radicals were, of course, founded upon 
the atomic theory of Dalton ; and as they were discussed and 
struggled over, and became more and more firmly intrenched 


in the science, they rendered the atomic theory an indispensa- 
ble assumption. Even when dualism became discredited, and 
organic chemistry took on a different significance from that of 
the chemistry of the compound radicals, atoms were still neces- 
sary, and the only changes were in the ideas as to the nature 
of the ultimate particles. 

The Substitution Theory and the Overthrow of Dualism 

Doubts began to arise as to the theory of dualism. Dumas and 
other chemists felt that Berzelius had pressed his theory too far. 
It was, however, the discovery of the principle of substitution 
which really dealt this theory its death-blow, and paved the 
way for the so-called unitary theory. Substitution might have 
been deduced from the old idea of equivalence. It was also 
really touched upon in the researches of Mitscherlich upon 
isomorphism. Other facts led up very nearly to it ; but, as so 
often happens, the thought itself was brought out by an acci- 

Substitution of Chlorine for Hydrogen In 1834 Dumas was 

called upon to examine into the cause of certain irritating 
vapors coming from wax candles used to illuminate the 
Tuileries. He found that, in bleaching the wax, chlorine had 
been used ; and some of the chlorine remaining in the candles 
had caused the disagreeable fumes, which consisted of hydro- 
chloric acid, the hydrogen coming from the wax. Dumas felt 
that this could not be explained on the ground of a mechanical 
retention of the chlorine as an impurity. He therefore fully 
investigated the action of chlorine upon wax and kindred 
organic substances. He announced, as a result of his investi- 
gations, that hydrogen in organic compounds can be exchanged 
for chlorine, volume for volume. Wohler and Liebig had, in 
1832, shown that, in preparing benzoyl-chloride out of bitter 
almond oil by the action of chlorine, two atoms of chlorine 


took the place of two atoms of hydrogen. This was contrary 
to the central idea of dualism ; for chlorine was electro-nega- 
tive, and ought never to substitute electro-positive hydrogen. 

Facts accumulated, however. Liebig had further shown 
that, by the action of bleaching powder and chlorine upon 
alcohol, chloroform and chloral could be produced. He misun- 
derstood the constitution of these bodies, and no one dreamed 
then of the wonderful part they were to play in alleviating 
pain and suffering. It was Dumas who correctly determined 
their nature and their relation to alcohol, showing here the far- 
going substitution of chlorine for hydrogen. Liebig promptly 
acknowledged his error. 

Trichloracetic Acid Dumas also, by his substitution of 

chlorine for hydrogen in acetic acid, forming trichloracetic 
acid, secured the most important support for his theory of 
substitution, which, as has been stated, he formulated one year 
later (1834). We can see from what Dumas says of trichlor- 
acetic acid what his ideas were as to substitution, and how 
the discovery of this acid supported them. 

It is well known that this acid differs from acetic acid 
by three atoms of chlorine substituted for three atoms of 
hydrogen. " It is a chlorinated vinegar," says Dumas ; " but 
it is remarkable, and the more so for those who dislike to 
find in chlorine a body capable of substituting hydrogen in 
the exact and full sense of the word, that this chlorinated 
vinegar is still an acid like ordinary vinegar. Its acid power 
has not been changed. It neutralizes the same amount of 
base as before. It possesses the same avidity; and its salts, 
compared with the acetates, show an agreement full of 

Conflict with the Dualistic Theory. _ Thus it was shown that 
the views of dualistic structure were too rigid, and were 


a hindrance to the development of organic chemistry. A 
negative atom could be substituted for a positive, and the 
compound radical began to be recognized as an atomic struc- 
ture in which one atom could be substituted for another with- 
out regard to its electrical relation. 

Laurent had convinced himself, by a great number of ex- 
periments, that Dumas' statement of the law of substitution 
did not hold good for all cases. Very often more chlorine 
was taken up, and sometimes less, than corresponded to the 
volume of hydrogen lost. As the substituted body showed 
certain analogies to the original, he maintained that the 
chlorine took the place held by the hydrogen in the molecule, 
and to a certain extent played the same role. 

Unitary Theory This view met with vigorous opposition, 

and had to be modified in some particulars ; but soon the 
molecule came to be regarded as a unitary structure, and not 
a dualistic. Thus, there were two opposed theories in chem- 
istry ; the older, dualistic, looked upon the molecules as 
double-natured and composite, yet forming one unchangeable 
whole in which the members lost their individuality, and the 
nature of these molecules was determined by the quality of 
the atoms ; the new, unitary, theory maintained that the num- 
ber of the atoms and their arrangement determined, in the 
main, the nature of the compound, and that this molecule was 
not unchangeable, but that the atoms comprising it could be 
substituted by others without a total change of nature. 

Nucleus Theory Laurent was led to propound, further, 

the nucleus theory, which was largely adopted, notably in 
Gmelin's handbook. This was in some respects an elabora^ 
tion of the idea of compound radicals ; indeed, Laurent calls 
his nuclei radicaux fondamentaux. Many of the ideas in 
this theory have been adopted and incorporated in the sci- 


ence, though the theory itself has been dropped. In this 
theory the nuclei were of different kinds. First there were 
combinations of carbon and hydrogen, in which the ratio of 
the elements was a simple one. For any one ratio there 
might be several of these radicals polymeric with one an- 
other. These were the stem nuclei ; and out of them, by the 
substitution of some other atom or group for hydrogen, 
secondary nuclei were formed. 

This theory manifestly sprang from the old radical theory, 
but with an important change ; namely, the radical here is 
not an unchanging group of atoms, but it is a combination 
which can be changed through the substitution of equiva- 
lents. It is but a step in the evolution of the modern theory, 
as seen in the benzen nucleus. The unimportant and the 
false have been stripped off, and the true has been retained. 

Type Theory Laurent and Gerhardt did much to up- 
build the unitary theory, and to introduce the new idea of 
types. These two friends well supplemented one another, 
and the joint work did much for the advancement of chemis- 
try. Laurent was speculative and full of theories, possessing 
the valuable quality known as scientific imagination. Ger- 
hardt was painstaking and accurate in his experiments, and 
paying more attention to details, supporting and confirming 
by his work the brilliant hypotheses of Laurent. Both were 
masters of the science. 

This new theory of theirs, that of the types, was, like the 
theory of radicals, quickly taken up, and soon became the 
central theory of the chemistry of the fifth decade. Accord- 
ing to Laurent, caustic potash was not a compound of oxide 
of potassium and water, but was rather to be looked upon as 
a derivative of water, being derived by replacing one atom of 
hydrogen in the latter by an atom of potassium. This was 
what was called the water type. Gerhardt recognized three 


types, water, hydrochloric acid, and ammonia, and tried to 
classify all compounds under one or the other of these types. 
Gradually it was seen that new types were necessary for newly 
discovered compounds, and the derivation from the types 
became more and more complicated. Organic chemistry, 
where this type theory was especially applied, became a 
Chemistry of Types, and was no longer one of Compound 

Berzelius, now an old man, contended most strenuously 
for his dualistic theory, and could not be reconciled to the 
change to the types and to the unitary theory. But the great 
master was engaged in a vain struggle. Even his favorite 
pupils deserted his side, and the " voice that once led no longer 
found an echo in science." 

Copulas and Conjugated Compounds In the course of this 

discussion, Berzelius formulated a new theory, as giving a 
better explanation of the substitution phenomena, and as 
being in better consonance with his theory of dualism. This 
was the theory of the conjugated compounds (gepaarte Ver- 
bindungen) a translation of the term accouplement introduced 
by Gerhardt in 1839, to designate a certain kind of union of 
organic with inorganic substances, in which both are united 
in an intimate combination, the characteristic properties of 
the components becoming no longer recognizable, the com- 
bining power of the one, as an organic acid, for instance, 
being retained. The other substance entering into the union 
was called by Gerhardt the Copule, and by Berzelius Paar- 
ling. The idea is not a very clear one. Berzelius endeavored 
to introduce it as best explaining many of the substitution 
processes. It gave him, often, very complicated formulas ; 
but, as he observed, the simplest are not always the right. 

To give an illustration, Berzelius thought, after Melsens 
had shown, in 1842, that the substitution derivative of acetic 


acid, chlor-acetic acid, could be changed back into the original 
acid, that acetic acid was a paired oxalic acid. Thus, its 
formula was written by him as C 2 H s . C 2 O s , and chlor-acetic 
acid was written C 2 Cl 8 . C 2 8 . This was practically giving 
up the fight, as by it he acknowledged that the Paarling, or 
copula, could undergo substitution, and that its exact nature 
did not have a predominating influence in determining the 
nature of the compound into which it entered. The idea was 
too complicated and difficult to carry out. 

Kolbe's Remodelling of the Radical Theory In the fifth 

decade, Kolbe endeavored to revivify the radical theory of 
Berzelius. This had been somewhat modified by its author, 
but had fallen into disrepute. Kolbe's modifications, as, 
for instance, in the unchanging nature of the radical and the 
idea of copulas, introduced by Berzelius, restored it some- 
what to favor. He strove to make this theory have a deeper 
bearing upon the constitution of organic compounds. His 
ideas as to copulas and conjugated compounds were changed 
several times, and were not very clear. Kolbe opposed 
strongly the theory of types. 


The substitution theory of Dumas, as developed by Lau- 
rent, led up naturally to the idea of the relative value of 
the atoms of the different elements. A comparison between 
these atoms was inevitable, as they were generally substituted 
for the same element, either hydrogen or oxygen. The quan- 
tities of the various elements thus substituting hydrogen were 
regarded as the equivalents, and up to the second half of the 
century there was much confusion between atoms and equiva- 
lents. A clearing up of this confusion was brought about by 


the important work of Frankland upon the saturation capaci- 
ties of the atoms. 

Frankland's Work upon the Organo-metallic Bodies The 

useless part of the radical theory was swept away by the 
work of Frankland upon the series of organic substances con- 
taining metals, known as the organo-metallic bodies. This 
work showed that the pairing of the radicals with the 
elements was to be explained on the ground of some char- 
acteristic property of the atoms. Upon these experiments 
Frankland founded the valence theory, the germ of which one 
can detect in much that has gone before, especially in the law 
of multiple proportions ; but the idea had not been clear, nor 
even expressed in a name, except by the vague term of " re- 
placement-value " introduced by Liebig. 

Polybasic Acids. — What is known as the doctrine of the 
polybasic acids contributed to the growth of ideas upon the 
subject of the saturation capacity. Gay Lussac, Gmelin, and 
many others had held the idea that in the metallic oxides one 
atom of metal was united with one atom of oxygen, and these 
oxides united with one atom of acid to form neutral salts. 
By Graham's researches upon the acids of phosphorus, it was 
shown that this view could be held no longer. He proved that 
in the ortho, pyro, and meta acids, for each " atom " of P 2 5 , 
there were three, two, and one " atoms " of " basic water " 
which could be substituted by equivalent amounts of metallic 
oxides. The saturation capacity of these acids was then 
dependent upon the "basic water" belonging to their constitu- 
tions. Liebig extended this to many other acids, and distin- 
guished between mono-, di-, and tri-basic acids. This term 
basicity, along with the ideas inherent in it, clung for some 
time to the theory of the valence, or saturation capacity, of 
the atoms. One sees in the above quotations from the work 
of Graham the confused use of the term atom. 


Atomicity of the Complex Radicals The idea of basicity 

was extended farther to the compound organic radicals. 
Thus Wurtz, in his paper upon the glycerine compounds, 
spoke of glycerine as a tribasic alcohol. Williamson noticed 
that the propyl radical differed from that of glycerine by 
having two more atoms of hydrogen, and thus, he reasoned, by 
the loss of two atoms of hydrogen a monobasic radical became 
a tribasic. He attached the idea of capacity for saturation or 
atomicity of the radical to the number of hydrogen atoms ca- 
pable of substitution. He called these radicals then monatomic, 
diatomic, etc. Wurtz' study of the amines also bore upon 
this point, and it is easy to see how the notion of atomicity 
was soon extended to the various compound radicals known. 

Introduction of the Idea of Valence According to Wurtz, 

the idea of valence was introduced into the science in three 
steps, as it were : — 

First, there was the discovery of the polyatomic combina- 

Secondly, the polyatomicity was referred to the state of 
saturation of the radicals. 

Thirdly, this notion of saturation was extended to the ele- 
ments themselves, which had first been applied to the radicals, 
and from this their atomicity was deduced. 

Deduction of Valence from Inorganic Compounds When one 

considers the formulas of the inorganic chemical compounds, 
even a superficial observer is attracted by the general symme- 
try to be observed in them. Especially do the compounds of 
nitrogen, phosphorus, antimony, and arsenic show the ten- 
dency on the part of these elements to form compounds in 
which three or five equivalents of other elements are contained. 
Without formulating a hypothesis to account for this agree- 
ment in the grouping of the atoms, it is sufficiently clear that 


a tendency to such regularity exists, and the affinity of the 
atoms of the above mentioned elements entering into combi- 
nation is always satisfied by the same number of atoms, without 
regard to their chemical character. 

Frankland did not consider a higher atomicity than five. 
Though he speaks of the simple inorganic compounds, and 
uses them in illustration, he deduced the valence doctrine 
from his studies of complex organic bodies. 

Progress made by the Valence Theory. . — These ideas did not 
meet with immediate acceptance. The type theory was still 
dominant, in spite of Kolbe's attacks upon it as something 
altogether unscientific. The discussion over the constitution 
of the polybasic acids and other atomic groups, joined in by 
Odling, Williamson, G-erhardt, Wurtz, and others, showed the 
neccessity for this theory, and did much to introduce it into 
the science. In a memoir published in 1855, Wurtz spoke of 
nitrogen and phosphorus as tribasic. By 1858 the theory had 
made rapid progress. In this year Kekule first deduced the 
valence of carbon from its simplest compounds, declaring it to 
be tetravalent. This had already been recognized by Kolbe 
and Frankland, if not expressly stated by them. But Kekule 
rendered further and much greater service by examining into 
the manner in which two or more of these tetravalent carbons 
were united with one another. The doctrine of atomic chains, 
open and closed, sprang from this, and the domination of the 
structural idea in chemistry became complete. 


The history of chemistry as a science for the thirty years 
just considered, that is approximately from 1830 to 1860, has 
consisted largely in an account of the rise and progress of one 
branch of it, namely, organic chemistry. The science was 


dominated by the theories deduced from the study of organic 
compounds, and we have seen how their number was multi- 
plied and the knowledge of them increased. 

Still, there was great and rapid growth along other lines. 
Great numbers of facts were accumulated and new bodies dis- 
covered. It becomes necessary to note briefly some of the ad- 
vances made since the wonderful work of Davy and Gay 

Discovery of New Elements. — Several new elements were 
added to the list, but it was not until the introduction of a 
new instrument of research in the spectroscope that many new 
ones were discovered. In 1817 Stromeyer discovered cadmium, 
and in the same year Arfvedson added lithium to the list. 
Berzelius first prepared silicon in 1822, and in 1827 and 1828 
his pupil Wohler succeeded in preparing aluminium and 
glucinum or beryllium. Balard added bromine in 1826, and 
then for thirty years we have no notable additions, with the 
exception of those gotten from the rare earths as yttrium, by 
Wohler, and several by Mosander. 

The Halogen Acids The list of halogen acids was com- 
pleted, Gay Lussac and Balard studying hydrogen bromide and 
hydrogen iodide, while Gay Lussac, Thenard, and Berzelius 
made many experiments upon hydrogen fluoride, learning much 
about its reactions. All attempts at separating fluorine from 
it were vain, but the energetic and dangerous nature of the 
acid was recognized. Later- on, experiments upon this body 
cost Nickles, a distinguished Swiss chemist, his life. Half a 
century later the element itself, fluorine, was isolated and 
studied by the French chemist Moissan. 

Allotropism. — The fact that an element could exist in 
several different forms has been partially recognized in the 
case of the different forms of carbon. It was now fully 


recognized in several other cases, as sulphur, phosphorus, 
arsenic, and oxygen. Berzelius gave to this phenomenon the 
name of allotropism. 

New Acids and Salts. — Of course the list of salts was 
greatly extended, especially with the discovery of new acids, 
and the recognition of differences in the capacities for satura- 
tion shown by these acids, or, as it is now styled, the different 
basicity of the acids. The discovery and study of the poly- 
basicity of acids marked an important step forwards. The 
excellent work of Graham and Liebig did much to clear up 
this matter. 

Permanent Gases Many important facts, physical and 

chemical, were learned about the gases. Most of them were 
condensed, especially by the experiments of Faraday, into 
liquids, or frozen into solids. Pressure was relied upon for 
this condensation, and little attention paid to the temperature. 
This ignorance of the important part played by the tempera- 
ture led to the belief that certain of them, as hydrogen, 
oxygen, nitrogen, methan, carbon monoxide, and nitric oxide, 
were uncondensable, and for these the term permanent gases 
was retained. 

Much later it was recognized that reduction of tempera- 
ture was necessary as well as pressure ; the critical temperature 
was studied by Andrews, and by the ingenious experiments 
of Pictet, and independently Cailletet (1877), all of the so- 
called permanent gases were condensed. 


The beginning of the century saw a blending of the two 
sciences of chemistry and physics along certain lines, a union 
of interests which promised and accomplished much for both. 


Thus, we have the application of electricity to chemistry, and 
the work of Ampere and Avogadro. This was followed by 
the work of Dulong and Petit. But the cultivation of this 
border land between the two was first systematically pur- 
sued by Kopp and Graham. The former devoted himself, 
after 1840, to the study of relations existing between atomic 
weights and specific gravities, regularities in boiling-points, 

Graham's Work The work of Graham deserves more ex- 
tended mention. In the first place, as has been stated, it is 
to him that we owe the conception of acids of different basi- 
city, and a confirmation of Davy's view that acids were com- 
pounds of negative oxides and water. He laid especial stress 
upon the necessity for the presence of hydrogen in all acids. 
This hydrogen was replaceable by metals, and was analogous to 
them ; and the molecule of the salt had the same general struc- 
ture as the acid from which it was formed. Thus Graham 
classed hydrogen for the first time with the metals, a bold 
step at the time, but one fully justified by the increased 
knowledge of later years. Graham also did some interesting 
work upon the subject of water of crystallization ; but his most 
important work was that bearing upon the physical side of 
chemistry, especially as to the motion of the ultimate particles 
of matter. These ultimate particles he called atoms, using 
this in pretty much the same way as Dalton did, not troub- 
ling himself to distinguish between atoms and molecules, as 
Avogadro had done, the distinction not being essential for his 
physical investigations. 

Diffusion Experiments Graham's chief work in this line 

was upon the diffusion of gases. He seems to have been led 
first to the investigation of the phenomenon, reported by 
Dobereiner, that jars having light cracks in them, when filled 


with hydrogen over water, showed a rise of the water in the 
jar, whereas, if filled with nitrogen, or oxygen, or air, there 
was no rise noted. Graham proved that some of the hydro- 
gen in the jar pressed outwards through the fissures, and but 
little air returned, therefore the pressure on the surface of 
the water outside was greater than inside, and the level 
rose inside. Any gas lighter than air behaved like hydro- 
gen. If heavier gases were used, the level inside was somewhat 

So Graham devised his diffusion tubes ; and, experimenting 
upon many gases, he announced the law of diffusion. From 
this he was led to examine the transpiration of gases, or their 
passage through capillary tubes, and in 1863 to his researches 
upon the molecular mobility of gases. 

Colloids and Crystalloids Graham also investigated the 

diffusion of liquids, and made application of this principle in 
analysis, particularly in regard to the dissolved solids in the 
liquids. Those diffusing readily he called crystalloids ; the 
non-crystallizable, jelly-like, slowly diffusing bodies were 
called colloids. On the basis of this classification, and the 
difference between these classes, is founded the principle of 

But Graham saw deeper into the nature of these bodies. 
He recognized the colloids as eminently unstable bodies, ever 
on the verge of change, and readily affected by changes of ex- 
ternal conditions ; in the crystalloids he saw more definite 
properties and a greater stability. 

Graham's life was largely spent in studying the move- 
ments of the particles of matter. As has been said of him : 
"A piece of lime or a drop of water was to the mind of 
Graham the scene of a continual strife ; for that minute por- 
tion of matter appeared to him to be constructed of almost 
innumerable myriads of little parts, each in more or less 


rapid motion, one now striking against another, and now 
moving free for a little space." 

The Spectroscope Physics again lent most efficient aid to 

chemistry by the introduction of the spectroscope as an in- 
strument for research. The introduction of this instrument 
created a sensation almost on a par with the first applications 
of the electric current by Davy and others to the same end. 
By it an examination of certain optical properties of highly 
heated bodies became possible. The extreme delicacy of the 
instrument permitted a deeper insight to be taken into the 
nature of the atoms, and has opened up an entirely new 
branch of stellar or extra-terrestrial chemistry. Thus it has 
become possible to learn something of the chemical constitu- 
ents of bodies outside of this earth. 

Spectrum Analysis The introduction of spectrum analy- 
sis is especially due to the labors of Kirchhoff and Bunsen, 
and the first discoveries date from the year 1860. It became 
especially useful in their hands for the discovery of new ele- 
ments, and for revealing the presence of traces of elements in 
various compounds, minerals, soils, etc., giving a truer idea of 
the natural occurrence of such, and an invaluable test for the 
purity of preparations. It opened up a new era of discovery 
of elements. Thus, we have rubidium and caesium dis- 
covered by Kirchhoff and Bunsen ; indium by Richter ; gal- 
lium by Lecoq de Boisbaudran ; thallium by Crookes ; and 
many rarer ones whose existence and properties have not yet 
been satisfactorily settled. Like other great discoveries, 
spectrum analysis was at first, perhaps, overestimated as to 
the part it would play in chemistry, but still it has been and 
is yet of very great service. 

Polariscope and Microscope The polariseope and micro- 


scope have also proved most valuable aids to chemical re- 
search, and it seems likely that these three instruments will 
prove of still greater value in aiding in the solution of the 
many unsolved questions connected with the nature and 
relations of the atoms. 


We will now take up again the development of the ideas 
as to the structure or constitution of chemical compounds, in 
particular those of organic chemistry. The valence theory, 
combined with the theories of radicals and types, led directly 
up to the structural chemistry of the last thirty years. 

The radical and the type theories were attempts at gaining 
an idea of the structure of chemical compounds ; but it was 
the valence theory which made it possible to give a clear 
answer to the question as to the constitution of such bodies. 
The determination of the structure or constitution of complex 
molecules became, with the beginning of the seventh decade, 
the higher aim of chemistry. 

New Systems of Classification Some beginnings of sys- 
tematic classification had already been introduced into organic 
chemistry, which greatly aided in the upbuilding of structural 
chemistry. Thus, the idea of homologous series, suggested by 
Schiel, was adopted by Dumas with regard to the fatty acids, 
and extended by Gerhardt. In 1849 there was the discovery 
of compound ammonias or amines, by Wurtz, and of mixed 
ethers by Williamson. Many systems of classification were 
suggested during the sixth decade, the classification by series as 
that of Schiel and Dumas, that of series depending upon for- 
mulas, series depending upon chemical behavior, and many 
other systems. The lack of agreement among chemists, how- 
ever, as to the formulas belonging to the different compounds, 


as to the relative weights of the molecules, the atomic weights, 
and even the number of atoms, prevented a general acceptance 
of any of the classifications proposed until Kekule established 
the fact of the tetravalence of the carbon atom, showed the 
difference between saturated and unsaturated compounds, and 
deduced his chain formulas. 

Atomic Chains Kekule's doctrine of the atomic chains 

was a necessary sequence of the valence theory. It was not 
necessary for this that the nature of valence or the cause of 
it should be known, and even yet no satisfactory solution of 
these questions has been offered. 

In 1866 Kekule offered his famous ring formula as an ex- 
planation of the nature of benzen, and the differences observed 
between its derivatives and those of the methan series. So 
great has been the influence exerted by this idea of a closed 
chain formula upon the development of organic chemistry 
and the great industries dependent on it, that twenty-five 
years later chemists from all parts of the world met in Berlin 
to do honor to the discoverer. And yet the details of struc- 
ture and of linkage in this closed chain of the benzen nucleus 
are still the subject of much discussion and multiplied 

While it is unquestionably true that the work done in 
examining into and determining the structure of organic 
bodies during the past quarter of a century has been so 
fruitful of results in the discovery of new substances and the 
synthesizing of natural products, that this younger branch 
of chemistry has far outstripped the older sister, and the 
shelves of libraries groan under the yearly added volumes, it 
must be constantly borne in mind that many of these struc- 
tural formulas are dependent upon very slender lines of 
reasoning, and doubt can be thrown upon some of them which 
seem to be most accurately determined. 


Physical Isomerism and Stereo-chemistry One of the dif- 
ficulties met with in the assignment of structural formulas 
lay in certain cases of isomerism. In some cases a greater 
number of isomeric bodies were known than could possibly 
be accounted for by any arrangement of the atoms in formulas 
upon a plane surface, retaining the accepted views as to 
valence, etc. Instances of these are the four isometric lactic 
acids, with only two arrangements of the formula possible, 
and the four tartaric acids with only two arrangements, and 
many other cases. As these bodies differed mainly in certain 
physical properties, they were at first somewhat vaguely 
styled physical isomers. 

The study of these led to what has been called the chem- 
istry of Space, or Stereo-chemistry, in which a wider view of 
atomic grouping was attempted. The foundations of the theo- 
ries as to the space relations of the atoms were laid by Van't 
Hoff and Le Bel, and much progress has been made in the last 
twenty years in filling out the outlines of this study. Among 
the most noted workers in this field have been Meyer, Bischof, 
Auwers, and others. 

Atomic Linkage It is manifest that the manner of union 

of atom with atom, or atomic linkage, is one of the most im- 
portant raised by the study of structural chemistry, and is most 
necessary to the proper understanding of it. There has been 
much written on this subject in the latter part of this century, 
and some preliminary work done ; but the whole question of 
linkage, as that of valence, is still a most puzzling one to 
chemists. The views as to the structure of double salts, of 
salts containing water of crystallization, and as to the charac- 
ter of the union in solutions and in alloys, are still very 



It has been seen how the atomic hypothesis became a 
necessity for the elucidation and development of organic chem- 
istry. It had fallen into disfavor because of the difficulties 
met with by Berzelius and others in distinguishing between 
atoms and molecules ; but much light was thrown upon this 
and other matters as the chemistry of the compounds of car- 
bon was better understood ; and the fact that the dominant 
doctrine of the new chemistry quietly assumed the truth of 
Dalton's theory in all its important particulars was reflected 
upon the older chemistry, so that this great theory became the 
basis for it all. 

Confusion in the Sixth Decade. — After Frankland's re- 
searches on the organo-metallic bodies, the old confusion 
between atoms and equivalents was done away with. Then, 
too, the value of Avogadro's law as an aid to the correct 
determination of atomic weights became more fully recog- 
nized, and analytical methods were much more accurate. The 
middle of the century saw the condition of affairs concerning 
these physical constants a badly mixed one. Two units or 
standards were in use. Dalton had suggested hydrogen as 
unity, and this standard was adopted by Gmelin and many 
others. Wollaston and Berzelius took oxygen as the standard, 
Wollaston giving it the value 10, and Berzelius using it as 100 ; 
Thomson had given it the value 1. But far worse than having 
two standards, widely differing values were assigned for the 
atomic weights, and all needed revision. In Germany, following 
Gmelin, many used the numbers H = 1 ; N = 14 ; CI = 35.5 ; 
C = 6 ; 0=8. Others used the Berzelian numbers, reduced for 
comparison to the same standard, H = 0.5 ; CI = 17.75 ; C = 6 ; 
0=8. Dumas, Laurent, and the French chemists used C = 3 ; 


Dumas' Revision of the Atomic Weights Dumas was espe- 
cially active in the revision of these numbers. His deter- 
mination of the atomic weight of carbon, and his work, in 
conjunction with Boussingault, to determine the ratio of 
hydrogen to oxygen in water, are classical. Dumas fixed the 
number sixteen for oxygen. This was afterwards determined 
as 15.96 by Stas ; and this ratio has been the subject of more 
painstaking and careful determinations than any other in 
chemistry, yet without complete accord. Dumas also deter- 
mined many other weights. 

The Work of Stas Others taking part in this work were 

Marchand, Marignac, De Ville, Scheerer, and Erdmann ; but 
easily the greatest of them all in care and accuracy was Jean 
Servais Stas. His work was monumental in the pains taken 
to secure absolute accuracy ; and yet in a few years errors were 
found in it, and the so-called Dumas' correction, as well as 
others, had to be applied to the numbers found by him. The 
atomic weights determined by him with the greatest care were 
those of silver, potassium, sodium, lithium, lead, chlorine, 
bromine, iodine, sulphur, nitrogen, and oxygen. 

Much of this work was undertaken to prove or disprove 
the correctness of Prout's hypothesis, based upon the elements 
having whole numbers for their atomic weights when hydro- 
gen was taken as unity. As the result of his work, Stas stated 
that he had found no confirmation for it. 

Continued Confusion of Standards. — Increased accuracy in 
the atomic weights has gradually led to the adoption of the 
fractional numbers found instead of the rounded-off integers. 
Lothar Meyer, in his "Modern Theories of Chemistry," took 
oxygen as 15.96, the number found by Dumas, instead of 16, 
previously accepted. This had been followed by Meyer and 
Seubert, in their table of the atomic weights as re-calculated 
by them, a book of wide authority. This move on the part of 


Meyer has had the unfortunate result of starting up once more 
the old contest between hydrogen and oxygen as the standard 
for the atomic weights ; and the chemistry of to-day finds two 
tables in use, one based on = 16, and the other onO = 15.96. 
These are more dangerous and troublesome because of the 
close approximation of the standards than if they were widely 
different. The general tendency has been toward the adoption 
of the former standard, = 16, and the abandonment of an at- 
tempt at unattainable accuracy in the matter of the oxygen- 
hydrogen ratio. This latter number must change with each 
new and improved determination of the ratio. Since most of 
the numbers for the other elements are determined by com- 
parison with oxygen, and so are dependent upon its atomic 
weight, it seems best to let that number be fixed, even though 
its choice be somewhat arbitrary. 

Cannizzaro's Revision Taking a step backward now to 

the middle of this century, we find that much of the credit of 
clearing away the difficulties attending the atomic weights, 
and placing them upon a more satisfactory footing, is due to 
Cannizzaro. He took a determined stand upon the necessity 
for the use of the law of Dulong and Petit, and Avogadro's 
statement of the law of volumes, in these determinations. He 
taught chemists to place reliance upon these methods, and so 
to correct many of the false atomic weights then in use. Thus 
an approximation to a correct table of atomic weights was 
secured, and the road opened up for the discovery of the great 
natural law underlying them. Cannizzaro's chief writings on 
the subject appeared in 1858. 

Numerical Relations Between the Atomic Weights For 

some time strange numerical relations between the atomic 
weights of various elements, even in their then imperfectly 
known condition, had been observed by many chemists. Es- 


pecially worthy of note are the work of Gmelin, the triads of 
Dobereiner (1829), and the more extended work of Petten- 
kofer, Dumas, and Cooke. But little attention was paid to 
these numerical curiosities. They seem to have been looked 
upon as mere jugglings with figures, or as having some hidden 
connection with Prout's hypothesis. 

Newlands* Law of Octaves But more important numerical 

regularities very soon became apparent, after a trustworthy 
table of atomic weights was provided by Cannizzaro. The 
first to give up the old alphabetical arrangement of the ele- 
ments, and suggest a table drawn up in the order of the 
atomic weights, was Newlands (1864). He deduced from this 
arrangement what he called the law of octaves, claiming that 
the elements when thus arranged fell into periods of seven, 
every eighth element showing analogous properties. How- 
ever faulty the periods as arranged by Newlands, it is clear 
that he recognized the two principles of the natural arrange- 
ment of the elements. 

Mendeleeff's Periodic Law Independently of Newlands, 

the same problem was worked out by the great Russian 
chemist, Mendeleeff ; and it was worked out far more system- 
atically and thoroughly by him, so that he is justly to be 
regarded as the originator and author of the periodic law. 
His papers appeared in 1S68, and in 1869, and later. 

The first announcements, as made by Newlands, were 
received with ridicule and soon forgotten ; but the chemical 
world was forced to take note of this great discovery by the 
genius of Mendeleeff, and of Lothar Meyer, who also worked 
out this law independently. 

Importance of this Law. — Soon it was known that, by 
means of Mendeleeff's table, atomic weights could be cor- 


rected, physical and chemical properties calculated, and, as a 
crowning achievement and confirmation, new elements to- 
gether with their properties predicted. Thus, scandium, 
gallium, and germanium were predicted by Mendeleeff, and 
other elements not yet discovered. 

Now all chemists recognize the dependence of the proper- 
ties of the elements upon the atomic weights, and the periodic 
law has become the central idea in the classification and 
study of the elements and their compounds. This law is the 
greatest discovery in chemistry since the announcement of 
Dalton's atomic theory, and has been much more rapidly 
accepted. It promises to lead up to results of the utmost 

Primal Elements Although the author of the periodic 

law would warn off investigators from any speculations as 
to the origin of the elements, the mysterious relationship 
revealed between them by the periodic law has naturally drawn 
the minds of men to thoughts not unlike those of the early 
philosophers who dreamed of the primal elements. For these 
can be only dreams so long as the facts to form a basis for 
their confirmation are lacking. Thus, we have the specula- 
tions of Crookes, and the spectroscopic work of Grtlnwald and 
Lockyer ; but such cannot be factors in the science of to-day. 


The chemistry of to-day is no longer analytical. That 
predominated during the first half of the century. Nor is it 
synthetical; the third quarter saw this rise to its highest 
point. Even the structural chemistry seems to have had its 
day, although these problems of structure are occupying more 
chemists to-day than any others. The great aim of chemistry 


is becoming, not the methods of tearing apart atoms, nor of 
building them up together, nor of settling their exact location 
in the molecule, nor their position in space, but far deeper 
than all of this, and carrying with it the explanation of it all, 
the nature of the atom itself. The molecule and its changes 
must be studied, for there is much to learn ; but with the 
sharper vision and the clearer knowledge gained through the 
toil of this nineteenth century the atom is becoming the point 
of attack. 

It can scarcely be hoped that the chemistry of the future 
will progress with the rapid leaps which the passing century 
has witnessed. Great generalizations will be worked out more 
slowly and painfully, because it has become almost impossible 
for one mind to grasp and master all of the broadened science. 
One man can hardly hope to be more than an analytical chem- 
ist, or an organic, or inorganic, or physical, or physiological, 
or agricultural, or technical chemist. The specialization of 
these different branches has gone on until they have become 
sciences in themselves. The periodicals publish vast and un- 
digested masses of new facts. As one has said, the " chemistry 
of to-day is overburdened with its facts." This intense special- 
ization may lead to the increased multiplication of facts and 
to minor discoveries, but it renders it more difficult to grasp 
the underlying laws. Such works as Meyer's " Modern Theo- 
ries of Chemistry " show the great difficulties that lie in the 
path of the future discoverer. 




The services of Boyle, Hoffmann, and Bergman, and later 
of Klaproth, Vauquelin, and Berzelius, in this field of analyt- 
ical chemistry, have already been briefly mentioned. Lam- 
padius published his " Handbook of Chemical Analysis of 
Minerals " in 1801 ; and other books followed this, showing a 
systematic arrangement of the methods then in use. The use 
of the blow-pipe was systematized and improved by Bergman, 
de Saussure, and notably Berzelius; and in later times this 
art of dry assay was greatly advanced by the well-known 
flame reactions of Bunsen. 

Followers of Berzelius Heinrich Rose and Wohler were 

especially active in working out the methods suggested by 
their great teacher, Berzelius, and in adding to and perfecting 
them. Berzelius had shown great ingenuity in the discovery 
of new methods, and he seemed to inspire his pupils with 
like powers. Stromeyer, Will, Liebig, Dumas, Thenard, 
Marignac, and many others have aided in the discovery of 
improved tests and better modes of separation and determi- 
nation, and in the invention of suitable apparatus for the many 
delicate operations. 

The Work of Fresenius The great master of chemical 

analysis, however, has been Remigius Fresenius, and for fifty 



years his life and labors have been devoted to this side of 
chemistry. In 1841, at the age of twenty-three, he was 
Liebig's assistant in Giessen. In 1848 he founded his labora- 
tory at Wiesbaden, devoted to analytical chemistry ; and this 
has been the training-school of many analysts from all parts of 
the world, and now employs a large force of teachers, and is 
visited by many students, while Fresenius still presides over it. 
His " Handbook of Qualitative Analysis " appeared first 
in 1841, and that of " Quantitative Analysis " in 1846. There 
have been published scores of editions and translations since, 
and these works have formed the basis for all modern litera- 
ture of the kind. Besides, Fresenius has given to the science 
great numbers of analyses of minerals, waters, and commercial 
products. Perhaps his greatest service has been the establish- 
ment of the " Zeitschrift fur Analytische Chemie," which has 
had a widespread circulation and influence since its first 
appearance in 1862. This has afforded a centre, a crystalliz- 
ing point, for all work pertaining to analysis. This first 
periodical has been followed by many similar publications in 
various countries and languages, but it still retains the first 

Associated Methods A glance at the recorded analyses 

of the past century will show great improvement in accuracy, 
rapidity, neatness, and ease as the decades have passed. The 
clumsy work of Dalton was greatly improved upon by Berze- 
lius ; yet his analyses not infrequently failed of the correct 
result by several integers, and were entirely out-classed by the 
work of Stas. The demand for accuracy has become greater, 
passing from the whole numbers of percentage to the decimals. 
The greatly improved methods enable even a tyro in these 
days to attain such closeness of results as was impossible for 
the earlier workers. 

Still, from inherent imperfections in the methods, and 


from differences in manipulations on the part of the chemists, 
there is much to be desired in the way of accuracy and 
uniformity. This last is of especial importance where large 
business interests are at stake, as in the settling of valuations 
of manufacturing materials and in taxation. Hence late years 
have seen the organization of analysts, and their repeated 
meetings for the selection of methods and the careful arrange- 
ment of all details of manipulation, so as to exclude, if pos- 
sible, all chance for variation. This co-operation in work, 
along sharply defined lines, is the latest phase in the develop- 
ment of analytical chemistry. 


In very early times there was an attempt at a classification 
of the soils according to fruitfulness, and also attempts at 
improving them by mixing, and by the addition of various 
manures. There was scarcely the foundation, however, for a 
systematic science until, during the last half of the eighteenth 
century, research and discovery along this line were stimu- 
lated by the offering of prizes by various French academies 
for methods of increasing the fertility of the soil. One of 
the first important writings upon this subject was the 
" Agriculture Fundamenta Chemica " (1761) of Wallerius, 
the Swedish chemist. 

The Humus Theory. — Toward the close of the last century 
a distinct school of agriculturists had sprung up. Thus in 
Germany, Albrecht Thaer, and in France, Dombasle, were 
leaders in advancing the idea that the fertility of the soil was 
due to the presence of humus, and that plants fed upon this 
and similar organic food in complete analogy with the nutri- 
tion of animals. The inorganic salts were unnecessary for 


the building up of the plant ; indeed, according to Thaer, it 
was possible that these " earths " were formed or created in 
the plant itself. Wallerius had endeavored to lay a much 
juster foundation for the science in a comparison between the 
constituents of the plants and of the soil upon which they 

The New Theory of Liebig. — The work of Priestley, Lavoi- 
sier, and de Saussure had thrown some light upon the relation 
of the plant to the atmosphere, but the old erroneous ideas as 
to plant nourishment received their death-blow at the hands 
of Liebig. The change of views was somewhat gradual, and 
came about through the discussion as to the reason for the 
improved yield of crops grown on lands treated with powdered 
bones. Thaer had maintained that burnt bones have simply 
the effect of lime. The good effect of the ordinary powdered 
bones was attributed to the gelatine and fatty matter, these 
being organic materials, and hence, according to the humus 
theory, the appropriate food for plants. Fawtier even main- 
tained that the " phosphate of lime, one of the components of 
the bones," could be neglected in considering the question of 
the increased fertility, " because it is indestructible and insol- 
uble." But the presence of phosphorus in seeds had been 
discovered by Polt, and confirmed by various chemists ; and in 
1840, supported by many experiments of his own and of his 
pupils, Liebig boldly stated the foundation principles of mod- 
ern agricultural chemistry. They were as follows : — 

1. Inorganic substances form the nutritive material for all 

2. Plants live upon carbonic acid, ammonia (nitric acid), 
water, phosphoric acid, sulphuric acid, silicic acid, lime, mag- 
nesia, potash, and iron ; many need common salt. 

3. Manure, the dung of animals, acts not through the or- 
ganic elements directly upon plant-life, but indirectly through 


the products of the decay and fermentative processes: thus 
carbon becomes carbonic acid, and nitrogen becomes ammonia 
or nitric acid. The organic manures which consist of parts of 
remains of plants and animals can be substituted by the inor- 
ganic constituents into which they would be resolved in the 

Field Trials Practical field trials, carried out by govern- 
ments and large land-owners, proved the truth of Liebig's 
deductions from his laboratory experiments; and the many 
investigators in this line since have mainly developed his 
ideas. Liebig's conclusion, that one must restore to the soil 
that which the removal of the crop had withdrawn, if one 
would prevent its exhaustion, is the basis of successful agri- 
cultural practice to-day. 

Other Investigators Boussingault had, independently of 

Liebig, arrived at the same or very similar conclusions. He 
also did much for the development of this new branch of 
science. Special attention was devoted to the chemical nature 
of the soil, its origin, the weathering of the original rocks, etc. 
The introduction of artificial manures was one great result of 
Liebig's work. In France this was more especially due to the 
labors of Boussingault and Ville. With this introduction and 
consequent demand for phosphates came a world-wide search 
for phosphatic materials, and the building up of the large in- 
dustry based upon their preparation and utilization. 

Agricultural chemistry employs now a large force of 
workers, and they are busied over many most important and 
interesting problems. Among these workers may be men- 
tioned Wagner, Warington, Grandeau, Johnson, and Wiley. 

The Experiment Stations. — It only remains to mention as 
a factor in the present and future growth of agricultural 


chemistry the experiment stations and laboratories established 
now by the governments of every civilized country. So great 
a number of trained scientific workers, whose entire time can 
be given to experiments and to researches, must bring about a 
great increase of knowledge in this very difficult field of work. 


The study, from a chemical standpoint, of the substances 
and processes in the animal body presents even greater diffi- 
culties and complexities than the similar study of plants. 
These two lines of study have been in a measure mutually 
helpful. At first the same chemists were often engaged in 
both, as de Saussure, Chevreul, Liebig, and others. They have 
now become very distinct and separate fields of research. 

The Problems to be solved In order to lay a foundation 

for physiological chemistry, it has been necessary first to have 
some knowledge of the multitudinous substances occurring in 
animal bodies, and, if possible, to learn the conditions under 
which these different bodies were formed. Several stumbling- 
blocks present themselves here. The delicacy and instability 
of many of these compounds, the possibility that their extrac- 
tion from the living organism or the killing of the organism 
might cause radical changes in them, and the extreme com- 
plexity and probable size of the molecules, which render 
it difficult to decide between the several possible formulas 
derived by analyses, are among the problems to be faced. Be- 
cause of the last-mentioned difficulty some of the most impor- 
tant substances occurring in animals have still no certain 
formula assigned them. Furthermore, there have, of course, 
been serious difficulties in the way of separation and purifica- 


Condition of the Science It is therefore not surprising 

that with these great problems before thern, the condition of 
life-chemistry should be in a far less satisfactory condition 
than that of the inanimate creation. Much valuable work 
has been done and many questions successfully solved. There 
is already a large and growing literature, and several periodi- 
cals are entirely devoted to the development of this great 
branch of knowledge, so important because of its intimate re- 
lations to our health and welfare. Some of the best-known 
workers are Brucke, Bernard, Hammersten, Traube, Hoppe- 
Seyler, Lehmann, Kuhne, Schiitzenberger, Thudichum, and 
Chittenden. It is impossible to do more than make mention 
of the names of these, without specifically describing the work 
of each. 

Fermentation and Decay Processes This most interesting 

branch of life-chemistry, leading up to the science of bacteri- 
ology, has been built up by the labors of Pasteur and Schiit- 
zenberger. Before it was known that yeast consisted of 
living cells, there was a mechanical-chemical theory as to 
these processes, especially that of alcoholic fermentation, 
devised by Liebig. This was proposed by him in 1839, and 
had many supporters. By this the yeast and such ferments 
were regarded as very unstable bodies ; and when they broke 
up, the shock of their decomposition was transmitted to the 
fermentable medium in which they were present, as, for in- 
stance, the dilute solution of sugar. 

Discovery of the Nature of Ferments Several investigators 

discovered, simultaneously and independently, that the yeast 
consisted of living organisms capable of self-multiplication. 
These discoverers were Schwann, Kiitzing, and Cagniard de 
Latour. This was followed by Pasteur's wonderful and 
epoch-making studies upon beer, wine, and vinegar, from 


which was deducted the vital or bacterial theory of fer- 
mentation. These discoveries and their development have 
had a far-reaching effect upon the wine and beer industries, 
upon agricultural science, and have revolutionized sanitary 
science and the theory of disease. 

The chemistry of these processes is, 'again, a very difficult 
one, and needs much research. Among the valuable results 
so far attained, we have the discovery of the ptomains or 
cadaveric alkaloids by Selmi, and their study by Otto, Huse- 
mann, Dragendorff, and Vaughan, and the interesting work 
upon the so-called tox-albumins found among the life products 
of these bacteria, and looked upon by some as possibly form- 
ing a means of immunity against certain diseases. 


A partial review of the advances in physical chemistry 
has already been given. Its progress has not been as rapid 
as it should have been, other branches of chemistry absorbing 
most of the attention of investigators ; but the future is much 
more promising. There seems to be an awakening in this 
direction. Only a few points can be touched upon here. 

Molecular Weight Determinations. — For a long time the 
only class of substances whose molecular weight could be 
determined were those which could be obtained in the form 
of a gas without decomposition. The older method for de- 
termining this, by weighing a measured volume of the gas 
under question, was improved upon by Hofmann, who meas- 
ured the volume of gas produced from a weighed quantity of 
substance ; and by Victor Meyer, who measured the volume 
of air or some indifferent gas displaced by the gas evolved. 
These methods were satisfactory for gaseous bodies, but left 


one in ignorance as to the molecular weights of a large num- 
ber of bodies which could not be turned into gases. 

Determination by Means of Freezing-Points and Boiling-Points. 

— Raoult described in 1883 his method of determining the 
molecular weights of solids by means of the lowering of the 
freezing-points caused by them in various solvents. Several 
years later V. Meyer drew attention of chemists to the great 
value of this discovery. Frequent use has been made of the 
method since. 

The use, for the same purpose, of the increase in the boil- 
ing-point caused by bodies in solution has been suggested and 
carried out by Beckmann and Wiley. 

Electro-Chemistry The foundations of electro-chemistry 

proper were laid by Joule's discovery of the relation subsist- 
ing between electrical and chemical energy, and further the 
work of Favre upon the same subject. Many have investi- 
gated the facts of electrical conductivity and resistance, but 
the greatest progress has been in the use made of electrolysis 
for analytical and industrial purposes. 

Electro-Chemical Analysis Liickow and Gibbs were the 

first to iptroduce the use of the electric current into chemical 
analysis, though work along the same line was done by Des- 
pretz, Jiloxam, and Nickles. Liickow (1865) proposed its use 
for the solution, detection, separation, and quantitative deposi- 
tion of metals, and the reduction of metallic compounds. The 
development of these processes is largely due to the labors of 
Hampe, Riche, Smith, and Classen. 

Electro-Metallurgy Jacobi announced in 1S39 the first 

industrial application of the deposition of metals by elec- 
tricity. The development was rapid. Much is due to the 


work of the Becquerels, Shaw, and Smee. Copper was first 
deposited, then many other metals, as silver, gold, and nickel. 
This forms the useful industry of electro-plating. 

Electro-chemical action is further used in the reduction of 
metals from their ores, their purification, and in the prepara- 
tion of such substances as phosphorus, caustic soda, chlorine, 
etc. The further extension seems most promising. 

Thermo-Chemistry That heat was disengaged in many 

chemical reactions has been long noticed ; and attempts were 
early made at measuring this, with the view of thus deter- 
mining the strength of the chemical force, or affinity, con- 
cerned in the reactions. There are many experiments of 
Lavoisier, Laplace, Rumford, and Davy on this subject, but 
they are imperfect. The instrument used in determining this 
heat of reaction, the calorimeter, was greatly improved by 
Favre and Silbermann, who made a valuable series of experi- 
ments upon heats of combustion. It has been also modified 
and improved by many chemists, as Regnault, Thomson, and 
Bunsen. The fundamental principle of thermo-chemistry, 
the constancy of the sum of the amounts of heat evolved, was 
laid down by Hess in the year 1840, though his work lay un- 
noticed for many years until it was brought into notice by 
Ostwald. Hess's work established the fact that the amount 
of heat evolved in any chemical reaction was always the same, 
whether the reaction was completed in one step, or broken up 
into several. Long before it had been deduced by Lavoisier 
and Laplace that the amount of heat required for the disso- 
ciation of a compound was equal to the amount produced by 
its formation. 

Thomson was the first to apply the mechanical theory of 
heat to thermo-chemical processes ; and he has for more than 
forty years been busy with the thermo-chemical examination 
of all important chemical reactions, adding an immense num- 


ber of facts to the knowledge of the subject. At one time a 
far greater importance was attached to these researches, and 
greater hopes held as to their outcome, than at present. Very 
distinguished chemists, as Berthelot, Stohmann, Ostwald, and 
Naumann, have been engaged in the work. The criticisms 
of Briihl have done much to show the imperfections of some of 
the deductions from thermo-chemical data. 

Photo-Chemistry The chemical action of light has at- 
tracted a good deal of attention from chemists. The synthe- 
sis of organic substances under the action of light in the cells 
of the living organisms is the most complex phase of this, but 
light causes a whole range of actions besides this. Complex 
or simple, they are not yet well understood. 

That side of the subject bearing upon the changes caused 
in certain metallic salts, as those of silver, has been more 
widely studied ; and this is what is more especially meant by 

Early Observations The singular action of light upon 

silver compounds was noted in very early times. Boyle had 
observed this darkening, but ascribed it to the air. Early in 
the eighteenth century Schultze had ascribed it to the real 
cause — the rays of light. Scheele examined the action of the 
different parts of the spectrum upon a layer of silver chloride 
spread upon paper, and proved that the violet rays were the 
ones causing the change. Davy was the first to make use of 
this for copying lights and shadows ; that is, for photograph- 
ing objects, but was unable to fix the image gotten. The dis- 
covery of the fixing agent in sodium thiosulphite by Herschel 
in 1836, of the first developing agent by Daguerre in 1839, 
and of the sensitizing agents by Talbot and others, laid the 
foundations for modern photography. 

But photo-chemistry means more than the study of the 


chemical processes involved in the taking of photographs. 
Draper instituted experiments looking to the measurement of 
the action of light, and the researches of Bunsen and Eoscoe 
added to the knowledge of actinometry. Vogel also aided in 
this work, and has done much for the science of photo-chem- 
istry. The absorption of chemically active rays, and what 
has been called photo-chemical induction, have also received 
attention from these chemists. 



Acids, nature of 98 

Acids, new theory of 100 

Adepts 39 

Aetherin theory 120 

Affinitas 27 

Affinity table of Bergman . . . 86 
Affinity table of Geoffroy .... 85 

Africanus 13 

Agricola 45, 46 

Agricultural chemistry .... 148-150 

Albertus Magnus 27 

Allotropism 132 

Alchemists 20-40 

Alchemists proper 35-40 

Alexandrian school, breaking up of 14 
Alkalies, decomposition of ... . 97 

Alkalizing principle 100 

Ampere 93, 112 

Among the ancients, chemistry . . 1-7 

Analytical chemistry 146-148 

Ancient alchemists 7-12 

Ancient views of nature 10 

Andrews 133 

Apparatus used by the ancients . . 15 

Aquinas, Thomas 28 

Arabians ... 20-25 

Arabists 25-32 

Arfvedson 132 

Aristotle ...... 11 

Aryan races 4 

Associated methods 147 

Atomic weights 140-144 

Auwers 139 

Avenzoar 25 

Averrhoes 25 

Avicenna 24 

Avogadro 112 

Avogadro's theory 93 

atomic chains 138 

itomic linkage 139 

Atomic theory 84-90 


Atomic theory confirmed .... 122 
Atomic theory extended ... .89 
Atomic weights of Berzelius . . 108, 111 
Atomic weights of Duraas . . . . 112 
Atomic weight determinations of 

Berzelius . . 103 

Atomic weight determinations of 

Dalton 90 

Atomicity 129 

Atomicity of complex radicals . . 130 
Atoms 87 

Baohuone, Arnold 31 

Bacon, Eoger ........ 28-30 

Bagdad university 20 

Balard 132 

Becher 56 

Beckman 154 

Beequerel 155 

Benzoic acid radical 120 

Bergman 68-70, 146 

Bergman's affinity table 86 

Bernard 152 

Berthelot 156 

Berthollet 84,85 

Berzelian theories 101 

Berzelius 101, 108, 118, 120, 121, 128, 133, 
140, 146 
Berzelius, determinations of atomic 

weights 103 

Berzelius's followers 146 

Berzelius's laboratory . ... 109 
Birth of chemistry ... 1 

Bischof 139 

Black 62, 63 

Bloxam 154 

Boerhaave . ... ... 60 

Boiling-points used to determine 

molecular weights . . . 154 

Boussingault 141, 150 

Boyle 53-55, 146, 156 





Brandt 68 

Briicke 152 

Briihl . . . 156 

Bunsen 136, 155, 157 

Cagniard de Latour . . . 152 

Cailletet ... 133 

Cannizzaro's revision of atomic 

weights 142 

Cavendish 63, 64 

Chaldeans ... .... 5 

Charlatans 38 

Chemical knowledge of the ancients 15 
Chemistry of the compound radicals 322 
Chemistry of the future . . .144 
Chevreul , . . 118, 151 

Chinese ... 4 

Chittenden ... . . 152 

Chlorine, true nature of . . . 99 

Classen ... . .... 154 

Classification of org. substances 119, 137 
Clement of Alexandria . . . 5, 7 

Colloids and crystalloids .... 135 

Combustion theory, Stahl . . 58 

Complex radicals, atomicity of 130 

Compound radicals, theory of . . 116 
Conjugated compounds . . 127 

Confusion in atomic weights . 140 

Confusion of standards ... .141 

Constancy of proportions . . 84 

Cooke . . . . 143 

Copulas 127 

Courtois . ... .99 

Cordova, University of . . . 21 

Cronsted-t ... 68 

Crookes . . . . . 136, 144 

Crystalloids . . . 135 

Cullen . . 62, 63 

Daguerre . .156 

Dalton . 87, 140 

Dalton's rules for atomic weights . 90 
Davy, Sir Humphry . . 95-101, 134, 156 
Davy's later life ... 101 

Decomposition by electricity 96 

Decomposition of the alkalies . . 97 
Decomposition of water . . 96 

Demokritos of Abdera ... 8 

Derivation of the name . 2 

Despretz . . 154 


Destruction of manuscripts ■ 4 

Development of organic chemistry. 115 

De Ville 141 

Dictionary of chemistry, first . . . 62 
Diffusion, experiments of Graham . 134 

Dimorphism ... 113 

Diocletian 4 

Discovery of new elements . . . . 132 

Dbbereiner 118,143 

Dombasle 148 

Draper 157 

Dragcndorff 153 

Dualistic theory 105 

Duhamel 61 

Dumas 120, 122, 123, 124, 125, 137, 140, 

141, 143, 146 
Dumas' revision of the atomic 

weights 141 

Dulong and Petit 110, 113 

Dyeing, ancient ........ 19 

Egyptians 5 

Electrical decomposition, first . 96 

Electro-chemistry 154 

Electro-chemical analysis .... 154 

Electro-chemical equivalents ... Ill 

Electro-chemical theory 105 

Electro-metallurgy 154 

Elements 81, 82 

Elements, discovery of new ... 132 

Elements of the Greek philosophers 10 

Eller 61 

English phlogistics 62 

Erdmann . . 141 

Experiment stations . . . . 150 

Faraday . . . . . ill 

Favre 155 

Fawtier .... .149 

Ferments . . . 152 

Fermentation and decay processes . 152 
Four-element theory ... .12 
Frankland . . . 129, 140 

Freezing-points used to determine 

atomic weights . . . 154 

French phlogistics 61,62 
Fresenius . . 147 

Gay Lussac . 91, 92, 118, 119, 129, 132 
Geber . .... 21-24 
Geoffroy . . .61 




GeofTroy, affinity table of ... . 85 

Gerharrtt 156, 127, 131, 137 

German phlogistics 55-61 

Glauber 49 


Glass-making, ancient . . . 

Gmelin 102, 113, 129,. 140, 143 


Gold-making, laws against . 
Gold-making traditions . . 

Graham 129, 133, 134 

Graham, diffusion experiments 
Graham's work . 


Greeks and natural science 

Greek papyri 

Greek philosophy . . 
Griinwald . . . 

Hammersten . . 


Halogen acids . . 
Helmont, John Van 


Hermetic art . 
Hermetic philosophers . 
Hermes Trismegistus . . 
Hess . . ..... 

Hoffmann . . 

Hofmann ... 


Hooke's theory of combustion 
Hoppe-Seyler .... 
Humus theory . . . 


Hydrochloric acid, composition of 
Hydrogen, discovery of 







. 144 









. 155 

59, 146 



. 62 

. 152 

. 148 




Iatro-chemists . . . . 
Indian races ... . 

Indestructibility of matter . . . 

Inscription of Hermes . . 
Introduction of the idea of valence 

Isomerism • 

Isomerism, physical . . . 




Jacobi .... 154 

Japanese ... 4 

Jewish alchemists 6 

Johnson, S. W 150 

Kekule 131, 138 

Kirchhoff 136 


Klaproth 94, 146 

Kolbe 128, 131 

Kopp 134 

Kuhne 152 

Kunckel 55 

Kutzing 152 

Lamp, perpetual 40 

Laplace . ... 155 

Latent heat, discovery of ... . 63 

Laurent 125, 126, 140 

Lavoisier 73-80, 118 

Lavoisier's views of organic chem- 
istry 115 

Leather, ancient . 19 

Lecoq de Boisbaudran . . . 136 

LeBel 139 

Lehmann .... 152 

Lemery .... . ... 57 

Lemery's division of chemical sub- 
stances 115 

Leyden papyri 3 

Libavius 45 

Liebig, 117, 120, 121, 122, 123, 124, 133, 147, 

149, 150, 151, 152 

Life force in organic chemistry . . 116 

Lockyer 144 

Lulli, Raymond 31 

Macquer 01 

Magnus 102 

Manuscripts, early 3 

Marchand . ... .... 141 

Marggraf 61 

Marignac . . ... 141, 146 

Medicaments, ancient 19 

Medicine, universal . . . 39 

Melsens 127 

Mendeleeff 143 

Metallurgy of the ancients . ... 16 
Meyer, L . . 141, 142, 143, 145 

Meyer, V 139, 153, 154 

Microscope 136 

Minerals and salts known to the 

ancients ... 18 

Mitscherlich Ill 

Mitscherlich, law of Ill 

Moissan 132 

Molecular weight determinations 153 

Mosander 102, 132 

Multiple proportions, law of . . . 89 




Muriatic acid, composition of . . . 98 
Mysticism 2 

Naumann 156 

Natural arrangement of the ele- 
ments 144 

Nature of ferments 152 

Neumann 61 

New appliances 108 

New elements 94 

Newlands 143 

New chemistry 80 

Nickles 132, 154 

Nucleus theory 125 

Numerical relations between atomic 

weights 142 

Octaves, law of 143 

Odling 131 

Olympiodorus 14 

Organic analysis ... ... 118 

Organic chemistry, development of, 116 

Organo-metallic bodies 129 

Organic substances classified ... 119 

Origin of metals 37 

Origin of theory of transmutation . 36 

Ostanes, the Mede 6 

Ostwald 155, 156 

Otto 153 

Overthrow of dualism 123 

Paracelsista 41-44 

Paracelsus 42-45 

Pasteur 152 

Periodic law 143 

Permanent gases 133 

Pettenkofer 143 

Phlogistic chemists 50 

Phlogiston theory ... . 51, 52 

Photo-chemistry 157 

Physical chemistry 153 

Physical isomerism 138, 139 

Physiological chemistry ..... 151 

Pictet 133 

Pneumatic Trough 65 

Polariscope 136 

Polt 149 

Polybasic acids 129 

Pott 61 

Pottery, ancient 18 

Priestley 64-68 


Primal elements 10, 144 

Problems of physiological chemistry 151 

Proust 88-95 

Prout's hypothesis .... 94, 141, 143 
Ptomains 153 

Qualitative chemistry .... 41 

Quantitative chemistry 73 

Quercetanus 45 

Quinta essentia 11 

Radical theory, changes in . . . 121 
Radical theory, extension of . .119,120 
Radical theory remodelled .... 128 

Raoult's method 154 

Regnault 155 

Revolution in chemistry .... 73-80 

Riche 154 

Richter 89, 136 

Roscoe 157 

Rose, G 102 

Rose, H , . 102, 146 

Rumford 155 

Saturation capacity 128 

Saussure 146, 151 

Science in the East 20 

Science in Spain 20 

Schaffer 68 

Scheele 70-72, 118, 156 

Scheerer 141 

Schiel 137 

Scholiasts 33-35 

Schiitzenbergcr 152 

Schwann 152 

Sennert 48 

Seubert 141 

Shaw 155 

Silbermann 155 

Smee 155 

Smith, E. F 154 

Soaps, ancient . . .... 19 

Solvent, universal ... . . 40 

Special branches of chemistry . 146-157 

Spectroscope . 13c 

Spectrum analysis 136 

Sphere of Demokritos 9 

Spread of the new chemistry . 82,83 

stahl 57-59 

Stas j 41 

Statique chimique, essai de ... 85 




Stereochemistry 138, 139 

Stohmann 156 

Stromeyer 132, 146 

Structural chemistry .... IIS, 139 
Substitution of chlorine for hydro- 
gen 123 

Substitution theory 123 

Suidas 2 

Swedish phlogistics 68-72 

Sylvius 60 

Symbols, Berzelian 104 

Symbols, Dalton's 105 

Symbols, introduction of .... 101 
Synesius 13 

Talbot 156 

Tanning, ancient 19 

Thaer, Albrecht 148 

Thermo-chemistry 155 

Thenard 132 

Thomson 89, 155 

Thudichum 152 

ThurncyBer 45 

Transference of learning to Arabia . 14 

Traube 152 

Trichloracetic acid 124 

Turquet de Mayerne 45 

Type theory 126 

Unitary theory 125 

Urea, synthesis of 118 


Valence 128 

Valence deduced from Inorganic 

substances 130 

Valence theory, progress of . . . 131 

Valentine, Basil 33-35 

Van't Hoff 139 

Vapor densities 112 

Vaughan 153 

Vauquelin 146 

Views of affinity 85 

Villanovanus, Arnold 31 

Ville 150 

Vitriol 27 

Vogel 157 

Volumes, law of 92 

Volume relations 90-94 

Wagner 150 

Wallerius 68, 149 

Warington 150 

Water, decomposition of ... . 96 
Watt's dictionary of chemistry . . 113 

Wiley 150, 155 

Will 146 

Williamson 131, 137 

Wfthler . . 102, 117, 118, 120, 123, 132, 146 
Wollaston 93, 112, 140 

Zosimus 2, 13 



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Accession no. 



Venable, F.P. 
A short history 
of chemistry. 

Call no. 5d ed .